A #Market-Based #Sentinel #Surveillance for an Early #Detection of Viral #Outbreaks

 

Abstract

Mexico has experienced recurrent viral epidemics of substantial intensity, including hyperendemic dengue, COVID-19, and recent reports of avian influenza A (H5N1) infections in birds, which pose an ongoing risk of zoonotic transmission. Mexico was also the location for the earliest detection of the pdmH1N1 virus during the 2009 influenza A pandemic. Under a One Health framework, markets represent a unique opportunity for low-cost virus monitoring at the human-animal interface. Under the hypothesis that these represent sentinel sites for an early virus detection, we implemented a pilot surveillance program at the central market of Merida city, Yucatan, Mexico, considered a regional hotspot for multiple and recent viral outbreaks. Longitudinal sampling was carried out over 11 months at 1-to-6-week intervals from April 2022 to February 2023. We used multi-type surveillance in mosquitoes, live poultry, and wastewater. All samples were screened using RT-qPCR. Positive samples for DENV, SARS-CoV-2 and avian influenza A were further sequenced and analysed under a phylogenetic and epidemiological approach. Through our entomological surveillance, we report the earliest detection of DENV-3 III-B3.2 (genotype III American II lineage, considered a major public health concern in Latin America) in Mexico, overlapping with the resurgence of DENV-3 as the predominant serotype driving the 2023 national epidemic, which showed an increased severity. Through wastewater surveillance, we consistently detect SARS-CoV-2 RNA in wastewater samples, coinciding with the two infection waves officially recorded at a city and state level. Finally, cloacal swabs taken from two juvenile birds at the market suggest that avian influenza A viruses circulated in live poultry sold at the market. These findings show that our market-based surveillance framework is effective for an early detection and monitoring of pathogenic viruses in urban settings, and could complement official epidemiological surveillance in low- and middle-income countries to strengthen early-outbreak warning systems.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This study was supported by the John Fell OUP Research Grant ATD00390 (M.E.Z and M.U.G.K), the Wellcome Infectious Disease Award ?317324/Z/24/Z (M.G.K, H.P.G and M.E.Z), the Secretaria de Ciencia, Humanidades, Tecnología e Inovación award (SECIHTI, Mexico) through the PRONACES Health grant (PRONAII project number 303002, G.S) and the Ciencia Básica y de Frontera programme (CBF2023-2024-3184, M.G.K), and the UKRI Innovation BSRC/EPSRC/NIHR 971557 grant (A.R.S). M.G.K is funded through a Sanger International Fellowship award. M.E.Z is funded by a UCL Rosetrees Excellence Fellowship UCL2024\2. P.M.D was funded through the doctoral program at ‘Posgrado en Ciencias de la Produccion y de la Salud Animal-UNAM’ through the SECIHTI doctoral scholarship. M.U.G.K. acknowledges funding from The Rockefeller Foundation (PC-2022-POP-005), Health AI Programme from Google.org, the Oxford Martin School Programmes in Pandemic Genomics & Digital Pandemic Preparedness, European Union's Horizon Europe programme projects MOOD (#874850) and E4Warning (#101086640), Wellcome Trust grants 303666/Z/23/Z, 226052/Z/22/Z & 228186/Z/23/Z, the United Kingdom Research and Innovation (#APP8583), the Medical Research Foundation (MRF- RG-ICCH-2022-100069), UK International Development (301542-403), the Bill & Melinda Gates Foundation (INV-063472) and Novo Nordisk Foundation (NNF24OC0094346). B.G is further funded by Wellcome Trust grants 303666/Z/23/Z, 226052/Z/22/Z & 228186/Z/23/Z. The contents of this publication are the sole responsibility of the authors and do not necessarily reflect the views of the European Commission or the other funders. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Source: 

Link: https://www.medrxiv.org/content/10.64898/2025.12.22.25342882v1

____

History of Mass Transportation: The Spoornet Class 14E Electric Locomotive

Von Col André Kritzinger, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11506789

Source: 

Link: https://de.wikipedia.org/wiki/Spoornet-Klasse_14E

____

History of Mass Transportation: The EC 250 ''Giruno'' Electric Multiple Unit Train

Par Daniel Wipf — Travail personnel, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=59022313

Source: 

Link: https://fr.wikipedia.org/wiki/EC_250_%C2%AB_Giruno_%C2%BB

____

A #VSV #vector #vaccine simultaneously targeting #H5N1 HA & M2 induces robust neutralizing and ADCC #antibody responses & provides full protection vs lethal #H5N1 infection in mouse model

 

Abstract

Human (avian) influenza A viruses, especially highly pathogenic avian influenza (HPAI) viruses, pose a significant public health threat, and a multivalent vaccine is the primary prophylactic measure to control these viruses. To establish such a vaccine, we generated two multivalent vesicular stomatitis virus (VSV)-based vaccine candidates (V-EtM2e/H505 and V-EtM2e/H522) and characterized their ability to induce protective immune responses. Our results revealed that vaccine immunization in mice induced high humoral immune responses against both the HPAI hemagglutinin (HA) protein and the ectodomain of M2 (M2e) protein. Intriguingly, vaccine-immunized mouse sera exhibited highly efficient neutralizing activity against the corresponding H5 pseudovirus and mediated potent and broad antibody-dependent cellular cytotoxicity (ADCC) activity against M2e derived from human and avian influenza H5, H1, H3, and H7 viruses. Furthermore, both intranasal and intramuscular immunization provided efficient protection against HPAI H5N1 virus challenge in mice, with a 100% survival rate and a nondetectable viral load in several tissues. Notably, noninvasive mucosal (IN) delivery of V-EtM2e/H522 achieved protection equal to that of IM delivery at a 100-fold lower immunizing dose. These findings provide strong evidence for the effectiveness of a multivalent VSV-based vaccine against human (avian) influenza A viruses.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Canadian Institutes of Health Research, https://ror.org/01gavpb45, (OS1-190775)

Social Sciences and Humanities Research Council of Canada (SSHRC), (CBRF2-2023-00217)

Global Affairs Canada, https://ror.org/0427vvt16, Canadian International Development Scholarship (BCDI2030)

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.26.696590v1

____

#Influenza #vaccination post - #COVID19 expands vaccine-specific effector #CD4 T-cells and Tregs under positive influence of host trained innate #immunity

 

Abstract

SARS-CoV-2 immunity and innate immune training may influence influenza vaccine immunogenicity. We investigated this in India. Adult volunteers with hybrid SARS-CoV-2 immunity were administered FluarixTM Tetra (GlaxoSmithKlein) 2022/2023 NH Vaccine in 2022. Significant induction of hemagglutinin inhibition-specific antibodies and polyfunctional central memory CD4+ T-cells (TCM) were observed 1-week post-vaccination with variable induction of CD8+T-cell and innate effectors. Vaccination also expanded Flu-specific regulatory T-cells (Treg), which negatively correlated with CD4 responses, highlighting vaccine immunogenicity may be subject to Treg dampening. FluarixTM did not boost SARS-CoV-2 immunity. However, SARS-CoV-2-specific T-cell responses correlated positively with vaccine-induced T-cell responses. We evaluated trained immunity post-COVID-19 as a potential regulatory mechanism linking SARS-CoV-2 and heterologous vaccine immunogenicity. We observed, elevated frequencies of basal bacterial Lipopolysaccharide (LPS)-induced IL-6+IL1β+HLA-DR+CD14+CD16- frequencies post-COVID-19 correlated positively with vaccine-induced Fluarix-specific CD4 T-cell frequencies. Our study highlights a potential positive role for COVID-19-driven immune imprinting on heterologous vaccine immunogenicity in a post-COVID-19 era.

Source: 

Link: https://www.nature.com/articles/s41541-025-01331-6

____

Genotype A3 #influenza #H5N1 isolated from fur #seals shows high virulence in #mammals, but not #airborne transmission

 

Abstract

The global spread of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b viruses has recently extended to include diverse mammalian species, raising new concerns about pandemic risk. In 2023, this clade was first detected in Russian marine mammals during a mass mortality event among northern fur seals in the Far East. Genetic analyses revealed the causative viruses to belong to genotype A3 of European origin, which is known to have circulated in wild birds across the Far East since 2022. Notably, these isolates harbor the mammalian-adaptive substitutions PB2-K482R and NP-N319K—mutations previously linked to enhanced virulence in non-H5 avian influenza viruses, but whose impact on A(H5N1) clade 2.3.4.4b viruses remained to be characterized. The heightened virulence of A3 genotype viruses is confirmed by data obtained via a mouse model. However, despite these adaptive changes, ferret transmission models showed no evidence of airborne transmission of the fur seal-derived virus. Our findings indicate that while PB2-K482R and NP-N319K may contribute to increased mammalian pathogenicity, they do not significantly increase the efficiency of respiratory transmission—a key prerequisite for human pandemic potential. Although suggesting a limited immediate pandemic threat from this A3 genotype, these results underscore the critical need for continued surveillance and functional assessment of emerging mammalian-adaptive mutations in circulating A(H5N1) viruses.

Source: 

Link: https://www.nature.com/articles/s41598-025-28032-3

____

#Macrolide #Resistance and P1 Cytadhesin Genotyping of #Mycoplasma pneumoniae during #Outbreak, #Canada, 2024–2025

 

Abstract

We investigated macrolide resistance and P1 genotypes of Mycoplasma pneumoniae during the 2024–2025 outbreak in Hamilton, Ontario, Canada. Macrolide resistance remained stable at ≈10%–20%, but significant shifts in P1 genotype distribution and resistance rates in P1 types occurred, indicating notable changes in M. pneumoniae molecular epidemiology in Ontario since 2011–2012.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/31/12/25-0872_article

____

#Effectiveness of the 2024–2025 #KP2 #COVID19 #vaccines in #USA during long-term follow-up

 

Abstract

Up-to-date estimates of COVID-19 vaccine effectiveness (VE) are needed to inform COVID-19 vaccination strategies and recommendations. This target trial emulation study aimed to estimate the long-term vaccine effectiveness (VE) of the 2024-2025 COVID-19 vaccines targeting the KP.2 Omicron variant within the Veterans Health Administration. The study population (90.9% male, mean age 70.7 years) included 538,631 pairs of vaccinated (i.e., received the KP.2 COVID-19 vaccine) and matched unvaccinated (i.e., did not receive the KP.2 COVID-19 vaccine) persons enrolled from August 2024 to January 2025. Over a mean follow-up of 172 days (range 97-232) extending to April 12, 2025, VE was low against laboratory-diagnosed SARS-CoV-2 infection (16.60%, 95% confidence interval [CI], 11.92-21.44), SARS-CoV-2-associated emergency department/urgent care (ED/UC) visit (21.05%, 95% CI, 14.22-27.21), SARS-CoV-2-associated hospitalization (19.53%, 95% CI 6.56-30.10) and much higher against SARS-CoV-2-associated death (65.53%, 95% CI 27.79-83.37). VE declined from 60 to 90 to 120 days against infection (31.28%, 25.81%, 22.44% respectively), ED/UC visit (34.40%, 29.19%, 25.71% respectively), hospitalization (37.39%, 28.98%, 22.52% respectively) and death (75.02%, 71.02%, 63.08% respectively). In conclusion, COVID-19 vaccines targeting the KP.2 variant used in the 2024-2025 season offered high protection against death and modest protection against infection, ED/UC visits or hospitalization, and VE declined over time.

Source: 

Link: https://www.nature.com/articles/s41467-025-67796-0

____

#MERS #Coronavirus - Global #update (#WHO D.O.N., Dec. 24 '25)

 

Situation at a glance

Since the beginning of 2025 and as of 21 December 2025, a total of 19 cases of Middle East respiratory syndrome coronavirus (MERS- CoV), including four deaths have been reported to WHO globally. 

Of the 19 cases, 17 were reported by the Kingdom of Saudi Arabia (KSA), and two were reported from France. 

Between 4 June and 21 December 2025, the Ministry of Health (MoH) of KSA reported a total of seven cases of MERS-CoV infection, including two deaths. 

In addition, at the beginning of December 2025, the National IHR Focal Point (IHR NFP) for France also reported two MERS-CoV travel – associated cases; involving individuals with recent travel to countries in the Arabian Peninsula. 

The notification of these latest cases does not change the overall risk assessment, which remains moderate at both the global and regional levels. 

These cases show that the virus continues to pose a threat in countries where it is circulating in dromedary camels, with regular spillover into the human population. 

WHO recommends implementation of targeted infection, prevention and control (IPC) measures to prevent the spread of health care-associated infections of MERS-CoV and onward human transmission.

Description of the situation

Since the first report of MERS-CoV in the KSA and Jordan in 2012, a total 2635 laboratory-confirmed cases of MERS-CoV infection, with 964 associated deaths (Case Fatality Ratio (CFR) of 37%), have been reported to WHO from 27 countries, across all six WHO regions (...). 

The majority of cases (84%; n=2224), have been reported from the KSA (...). 

Since the beginning of 2025 and as of 21 December, a total of 19 cases have been reported to WHO. 

Overall, 17 cases were reported in the KSA from five regions named: Riyadh (n=10), Taif (n=3), Najran (n=2), Hail (n=1), and Hafr Al-Batin City (n=1) (...). 

In addition, two travel associated cases of MERS-CoV infection have been reported in France, with likely exposure occurring during recent travel in the Arabian Peninsula (...). 

This disease outbreak news report focuses on the recent nine cases of MERS-CoV infection reported between 4 June - 21 December 2025: seven cases from the KSA and the two imported cases to France. 

The details of cases reported earlier in 2025 can be referred to in the previously published disease outbreak news on 13 March 2025 and 12 May 2025.

Between 4 June and 21 December 2025, the MoH of the KSA reported a total of seven cases of MERS CoV infection. 

The cases were reported from three regions: Najran (2), Riyadh (3), and Taif (2). 

No epidemiological links were identified between the seven cases. 

In addition, between 2 and 3 of December 2025, the IHR NFP for France reported two cases of MERS – CoV with recent travel to the Arabian Peninsula during the month of November.

Follow-up has been completed for all contacts and no secondary infections have been identified or reported. 

From September 2012, France has recorded a total of four laboratory-confirmed cases of MERS-CoV infection, including one death: two cases were reported in 2013, and the latest two cases in December 2025. 

All cases had been travelers exposed in the Arabian Peninsula and returning back to France.

(...)

Epidemiology

Middle East respiratory syndrome (MERS) is a respiratory illness caused by a coronavirus (MERS-CoV). The case fatality ratio (CFR) among confirmed cases is around 37%. The CFR is calculated based solely on laboratory-confirmed infections and may overestimate the actual mortality rate since milder cases often go undetected or unreported.

Humans can contract MERS-CoV through multiple transmission pathways; the primary route being through direct or indirect contact with dromedary camels, which serve as the virus’s natural host and primary zoonotic reservoir. 

Additionally, human-to-human transmission can occur via infectious respiratory particles primarily in close-contact situations and can also occur through direct or indirect contact; this is especially prominent in health-care settings. 

Human-to-human transmission of the virus has occurred in health care facilities in several countries, including transmission from patients to health care providers and transmission between patients before MERS-CoV was diagnosed. 

It is not always possible to identify patients with MERS‐CoV early or without testing because symptoms and other clinical features may be non‐specific. 

Outside these environments, there has been limited documented human-to-human transmission. 

MERS can present with no symptoms (asymptomatic), mild symptoms (including mild respiratory issues), or severe illness leading to acute respiratory distress and death. 

Common symptoms include: 

- fever, 

- cough, and 

- breathing difficulties, 

- with pneumonia frequently observed, though not always present. 

Some patients also experience gastrointestinal symptoms such as diarrhoea. 

Severe cases may require intensive care, including mechanical ventilation. 

Those at higher risk of severe outcomes include older adults, individuals with weakened immune systems, and those with chronic conditions like diabetes, kidney disease, cancer, or lung disorders.

The number of MERS-CoV infections reported to WHO substantially declined since the beginning of the COVID-19 pandemic. 

Initially, this was likely the result of epidemiological surveillance for SARS-CoV-2 being prioritized. 

Similar clinical pictures of both diseases may have resulted in reduced testing and detection of MERS-CoV infections. 

However, the MoH of the KSA has been working to improve testing capacities for better detection of MERS-CoV since the easing of the COVID-19 pandemic, with MERS-CoV included into sentinel surveillance testing algorithms since the second quarter of 2023, for samples that test negative for both influenza and SARS-CoV-2. 

In addition, recommended IPC measures (e.g., mask-wearing, hand hygiene, physical distancing, improving ventilation) and public health and social measures in the community to reduce SARS-CoV-2 transmission, (stay-at-home orders, reduced mobility) also likely reduced onward human-to-human transmission of respiratory infections including MERS-CoV. 

Potential cross-protection conferred from infection with or vaccination against SARS-CoV-2 and any reduction in MERS-CoV infection or disease severity and vice versa has been hypothesized but requires further investigation. [1,2]  

Public health response

WHO is supporting Member States in strengthening preparedness and response.

Activities in the Kingdom of Saudi Arabia include:

-- Strengthened surveillance with immediate notification of all suspected and confirmed cases.

-- Strict implementation of infection prevention and control transmission-based precautions (Contact and Droplet precautions) in healthcare facilities for suspect or confirmed patients, and airborne precautions for patients undergoing aerosol-generating procedures.

-- Identification of health and care worker contacts and perform risk assessment of their exposure, considering the timely identification of symptomatic patients, implementation of IPC measures, and correct utilization of PPE while treating patients,

-- Exposed health and care workers are followed up for 14 days to monitor symptoms. If they develop symptoms, they are to be removed from working with patients until tested and symptoms are fully resolved.

-- Patients exposed to MERS-CoV in the healthcare setting must be tested to determine their ability to continue working with patients without further transmission, which could potentially lead to outbreaks in the healthcare facility. 

-- Identification of all potential community contacts and active follow-up to monitor symptoms for 14 days.

-- All community acquired cases are investigated for having direct or indirect contact with camels or their products.

-- Cases linked to camel exposures are notified to the National Center for Prevention and Control of Plants, Pests, and Animal Diseases (Weqaa) to investigate potential camel sources.

-- Camels identified as a presumed source are quarantined and tested for MERS-CoV, and if live virus is detected, the quarantine period will be extended until live virus is no longer detected in camel.

Activities in France include:

-- On 4 December 2025, MoH France published information regarding the two imported cases of MERS-CoV in the country.

-- Genomic sequencing was conducted from the first case and reported as being the same lineage that is circulating in the Arabian Peninsula. Further laboratory analyses are ongoing.

-- Contact tracing was initiated as soon as the first case was detected for the monitoring and surveillance of fellow travellers and co-exposed individuals, high-risk contacts, and hospital contacts. It was completed in week 51 and no additional cases among the travellers have been reported, nor any secondary cases as of 19 December 2025. 

-- Asymptomatic co-exposed individuals and at-risk contacts located in France were offered a full testing protocol (nasopharyngeal swab, sputum, rectal swab and serology) on a voluntary basis up to 29 days after their last exposure, even if they did not exhibit any symptoms.

WHO risk assessment

As of 21 December 2025, a total of 2635 laboratory-confirmed cases of MERS-CoV infection have been reported globally to WHO, with 964 associated deaths. 

The majority of these cases have occurred in countries on the Arabian Peninsula, including 2224 cases with 868 related deaths (CFR 39%) reported from the KSA.

A notable outbreak outside the Middle East occurred in the Republic of Korea, in May 2015, during which 186 laboratory-confirmed cases (185 in the Republic of Korea and 1 in China) and 38 deaths were reported. However, the index case in that outbreak had a history of travel to the Middle East.

Three limited healthcare-related clusters have recently been reported from the KSA, two in 2024 comprised of three and two cases each, and one in 2025 comprised of 7 cases; the previous cluster before that had been observed in May 2020, also in the KSA. 

Extensive contact tracing was applied in the 2025 cluster, which lead to detection of four asymptomatic and two mild cases, who fully recovered. 

Despite these recent clusters, zoonotic spillover remains an important mode of human infection, leading to isolated cases and limited onwards transmission between humans.

Global total cases reflect laboratory-confirmed cases reported to WHO under IHR (2005) or directly by Ministries of Health from Member States. These figures may underestimate the true number of cases if some were not reported to WHO, as they may be missed by current surveillance systems and not be tested for MERS-CoV – either due to similar clinical presentation as other circulating respiratory diseases or because infected individuals remained asymptomatic or had only mild disease. The total number of deaths includes those officially reported to WHO through follow-up with affected Member States. 

The notification of these new cases does not change the overall risk assessment. 

WHO expects that additional cases of MERS-CoV infection will be reported from the Middle East and/or other countries where MERS CoV is circulating in dromedaries, and that cases will continue to be exported to other countries by individuals who were exposed to the virus through contact with dromedaries or their products (for example, consumption of raw camel milk,  camel urine, or eating meat that has not been properly cooked), or in a healthcare setting. 

Due to the similarity of symptoms with other respiratory diseases that are widely circulating, like influenza or COVID-19, detection and diagnosis of MERS cases may be delayed, especially in unaffected countries, and provide an opportunity for onward human-to-human transmission to go undetected. 

WHO continues to monitor the epidemiological situation and conducts risk assessments based on the latest available information.  

No vaccine or specific treatment is currently available, although several MERS-CoV-specific vaccines and therapeutics are in development. 

Treatment remains supportive, focusing on managing symptoms based on the severity of the illness.

WHO advice

-- Surveillance:

- Based on the current situation and available information, WHO re-emphasizes the importance of strong surveillance by all Member States for acute respiratory infections, with the inclusion of MERS-CoV into the testing algorithm where warranted, and to carefully review any unusual patterns.  

-- Clinical Management:

- The incubation period is typically 2-15 days (median 5 days), although prolonged incubation periods have been reported in the immunocompromised. 

- Although mild disease does occur, clinicians should be aware that symptoms may frequently progress rapidly non-specific signs of upper respiratory tract infection, cough and breathlessness, to respiratory failure and cardiovascular collapse.[3]

- MERS-CoV infection should be managed supportively with respiratory support titrated to the needs of the patient; there is a wide spectrum of severity, with many patients requiring mechanical ventilation.

- The largest clinical trial in MERS compared a combination of lopinavir–ritonavir and interferon β-1b with placebo (95 patients).[4] 

- Active treatment caused lower 90-day mortality in hospitalized patients with laboratory-confirmed MERS (90-day mortality of 48% and 29% respectively). 

- Further analysis suggested a positive effect only in patients treated within 7 days of symptom onset. 

- Although there is increasing use of corticosteroids for some respiratory conditions (specifically in COVID-19 and some other forms of pneumonia), their use in MERS-CoV is of uncertain benefit, and harms relating to their immunomodulatory effects may be significant; more data are needed. 

- The use of convalescent plasma has not been proven, although has been used in a limited number of patients in a non-trial setting. 

- While antibiotics have been used in severe disease to presumptively treat concurrent bacterial infection, there are no controlled data on efficacy. 

- A retrospective analysis of 349 MERS patients examined macrolide antibiotic therapy. No difference in 90-day mortality was found in the 136 patients receiving macrolides compated with those who did not.[5]

-- Infection prevention and control:

- Human-to-human transmission of MERS-CoV in healthcare settings has been associated with delays in recognizing the early symptoms of MERS-CoV infection, slow triage of suspected cases and delays in implementing timely IPC measures. 

- IPC measures are therefore critical to prevent the spread of MERS-CoV in healthcare facilities and onwards in the community. 

- Healthcare workers should always apply standard precautions consistently with all patients and perform risk assessments at every interaction in healthcare settings to determine the necessary protection measures. 

- For patients with suspected MERS-CoV infection that require hospitalization, place patient in an adequately ventilated single room away from other patient care areas. 

- In addition to standard precautions. Droplet and contact precautions should be implemented when providing care to patients with symptoms of acute respiratory infection who are suspects of any respiratory disease, including probable or confirmed cases of MERS-CoV infection.[6,7]

- Droplet and contact precautions should be maintained until the patient is no longer symptomatic (for at least 24 hours) and has two upper respiratory (URT) swabs (taken 24hrs apart) test negative in RT-PCR or according to local guidance. 

- Additionally, airborne precautions should be applied when performing aerosol generating procedures or in settings where aerosol generating procedures are conducted. 

- Early identification, case management and prompt isolation of suspected respiratory infected patients and cases, quarantine of contacts, together with appropriate IPC measures in health care settings, including improving ventilation in enclosed spaces and public health awareness can prevent the spread of human-to-human transmission of MERS-CoV. 

-- Public health and social measures:

- MERS-CoV appears to cause more severe disease in people with underlying chronic medical conditions such as diabetes, renal failure, chronic lung disease, and immunosuppression. 

- Therefore, people with these underlying medical conditions should avoid close contact with animals, particularly dromedaries, when visiting farms, markets, or barn areas where the virus may be circulating.

- General hygiene measures, such as regular hand hygiene before and after touching animals or animal products and avoiding contact with sick animals, should be adhered to. 

- In addition, hygiene practices should be observed including the five keys to safer food should be followed when dealing with food items of camels; people should avoid drinking raw camel milk or camel urine or eating meat that has not been properly cooked. 

- WHO does not advise special screening at points of entry with regard to this event, nor does it currently recommend the application of any travel or trade restrictions. 

Further information

-- Infection prevention and control during health care for probable or confirmed cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection:interim guidance: updated October 2019.   [Internet]. [cited 2025 Dec 10]. Available from: https://iris.who.int/handle/10665/174652

-- Transmission-based precautions for the prevention and control of infections: aide-memoire [Internet]. [cited 2025 Dec 10]. Available from: https://iris.who.int/handle/10665/356853.

-- Standard precautions for the prevention and control of infections: aide-memoire.[cited 2025 Dec 10] Available from https://iris.who.int/handle/10665/356855

-- MERS fact sheet, updated 11 December 2025. Available from: https://www.who.int/news-room/fact-sheets/detail/middle-east-respiratory-syndrome-coronavirus-(mers-cov)

-- 2015 MERS outbreak in Republic of Korea [Internet]. [cited 2025 Dec 10]. Available from: https://www.who.int/westernpacific/emergencies/2015-mers-outbreak

-- WHO MERS-CoV dashboard. [cited 2025 Dec 10]. Available from: https://data.who.int/dashboards/mers

-- Disease Outbreak News [Internet]. [cited 2025 Dec 10]. Available from: https://www.who.int/emergencies/disease-outbreak-news

-- EPI-WIN webinar: MERS-CoV, a circulating coronavirus with epidemic and pandemic potential - Pandemic preparedness, prevention and response with a One Health approach [Internet]. [cited 2025 Dec 10]. Available from: https://www.who.int/news-room/events/detail/2023/05/24/default-calendar/epi-win-webinar-mers-cov-a-circulating-coronavirus-with-epidemic-and-pandemic-potential-pandemic-preparedness-prevention-and-response-with-a-one-health-approach

-- MERS Outbreak Toolbox [Internet]. [cited 2025 Dec 10]. Available from: https://www.who.int/emergencies/outbreak-toolkit/disease-outbreak-toolboxes/mers-outbreak-toolbox

-- Middle East Respiratory Syndrome (MERS) | Policy&Services : KDCA [Internet]. [cited 2025 Dec 10]. Available from: https://www.kdca.go.kr/contents.es?mid=a30329000000

-- Middle East respiratory syndrome: global summary and assessment of risk - 16 November 2022 [Internet]. [cited 2025 Dec 10]. Available from: https://www.who.int/publications/i/item/WHO-MERS-RA-2022.1

-- OpenWHO.org - Middle East respiratory syndrome [Internet]. [cited 2025 Dec 10]. Available from: https://openwho.org/channel/Middle+East+respiratory+syndrome/574814

-- Practical manual to design, set up and manage severe acute respiratory infections facilities [Internet]. [cited 2025 Dec 10]. Available from: https://iris.who.int/items/eb2cb9aa-ef45-4952-8307-a00cbeee70a6

-- Strategic plan for coronavirus disease threat management: advancing integration, sustainability, and equity, 2025–2030 [Internet]. [cited 2025 Dec 10]. Available from: https://www.who.int/publications/i/item/9789240117662

-- Update 88: MERS-CoV, a circulating coronavirus with epidemic and pandemic potential - Pandemic preparedness, prevention and response with a One Health approach [Internet]. [cited 2025 Dec 10]. Available from: https://www.who.int/publications/m/item/update-88-mers-cov-a-circulating-coronavirus-with-epidemic-and-pandemic-potential-pandemic-preparedness--prevention-and-response-with-a-one-health-approach

-- WHO EMRO - MERS outbreaks [Internet]. [cited 2025 Dec 10]. Available from: https://www.emro.who.int/health-topics/mers-cov/mers-outbreaks.html?format=html 

References:

[1] AlKhalifah, J. M., Seddiq, W., Alshehri, M. A., Alhetheel, A., Albarrag, A., Meo, S. A., Al-Tawfiq, J. A., & Barry, M. (2023). Impact of MERS-CoV and SARS-CoV-2 Viral Infection on Immunoglobulin-IgG Cross-Reactivity. Vaccines, 11(3), 552. https://doi.org/10.3390/vaccines11030552

[2] Zedan, H. T., Smatti, M. K., Thomas, S., Nasrallah, G. K., Afifi, N. M., Hssain, A. A., Abu Raddad, L. J., Coyle, P. V., Grivel, J. C., Almaslamani, M. A., Althani, A. A., & Yassine, H. M. (2023). Assessment of Broadly Reactive Responses in Patients With MERS-CoV Infection and SARS-CoV-2 Vaccination. JAMA network open, 6(6), e2319222. https://doi.org/10.1001/jamanetworkopen.2023.19222

[3] Middle East respiratory syndrome, Memish, Ziad A et al. The Lancet, Volume 395, Issue 10229, 1063 – 1077

[4] Arabi, Y. M., Asiri, A. Y., Assiri, A. M., Balkhy, H. H., Al Bshabshe, A., Al Jeraisy, M., Mandourah, Y., Azzam, M. H. A., Bin Eshaq, A. M., Al Johani, S., Al Harbi, S., Jokhdar, H. A. A., Deeb, A. M., Memish, Z. A., Jose, J., Ghazal, S., Al Faraj, S., Al Mekhlafi, G. A., Sherbeeni, N. M., Elzein, F. E., … Saudi Critical Care Trials Group (2020). Interferon Beta-1b and Lopinavir-Ritonavir for Middle East Respiratory Syndrome. The New England journal of medicine, 383(17), 1645–1656. https://doi.org/10.1056/NEJMoa2015294

[5] Macrolides in critically ill patients with Middle East Respiratory Syndrome, Arabi, Yaseen M. et al., International Journal of Infectious Diseases, Volume 81, 184 - 190

[6] Infection prevention and control during health care for probable or confirmed cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection. Available at https://www.who.int/publications/i/item/10665-174652

[7] Transmission-based precautions for the prevention and control of infections: aide-memoire. Available at: https://www.who.int/publications/i/item/WHO-UHL-IHS-IPC-2022.2

Citable reference: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON591

Source: 

Link: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON591

____

#Italy - #Influenza A #H5 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

{Eurasian Teal}

{Eurasian Wigeon}

{Mute Swan}

___

This is a new event opened to report outbreaks for which the N subtype could not be determined due to insufficient diagnostic material; in these cases, only the presence of H5 can be confirmed.

Three Common Teals (Friuli Venezia Giulia, Lombardy) , two Eurasian Wigeons (Friuli Venezia Giulia), one Mute Swan (Lombardy). 

Source: 

Link: https://wahis.woah.org/#/in-review/7144

____

#Brazil - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

The Official Veterinary Service (OVS) of the state of Mato Grosso received a notification of a suspected case influenza A viruses of high pathogenicity in domestic birds from a multi-species backyard, on December 20, 2025. Official Laboratory (LFDA-SP) analysis confirmed the presence of the H5N1 virus, clade 2.3.4.4b. The premises have been placed under quarantine. Birds will be culled, and carcasses, products, and any potentially contaminated materials will be destroyed. The OVS is currently conducting an epidemiological investigation in the surrounding area.

Source: 

Link: https://wahis.woah.org/#/in-review/7147

____

Emergence of D1.1 #reassortant #H5N1 avian #influenza viruses in North #America

 

Abstract

Since 2021, highly pathogenic avian influenza viruses (HPAIV) belonging to H5N1 clade 2.3.4.4b have caused high mortality in North American wild birds and poultry. In 2025, a new D1.1 genotype caused two human deaths and host-switched to dairy cattle. However, the evolutionary origins and dynamics of D1.1 have not been fully characterized. Here, our phylogenetic analysis of 17,516 H5N1 genome sequences uncovers how D1.1 introduced a major shift in the antigenic diversity and ecology of the H5N1 epizootic in North America. D1.1 is the first major H5N1 genotype to (a) emerge in the Pacific flyway and spread west-to-east faster than any prior genotype; (b) antigenically shift via reassortment with the North American N1 segment, displacing the previously fixed Eurasian N1; and (c) transmit to a broader range of host species than any H5N1 genotype to date, introducing mammalian adaptations.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Research Foundation - Flanders, https://ror.org/03qtxy027, G098321N, G0E1420N

European Union Horizon 2023 RIA project LEAPS, 101094685

DURABLE EU4Health project 02/2023-01/2027, 101102733

Fonds National de la Recherche Scientifique, F.4515.22

European Union Horizon 2020 project MOOD, 874850

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.19.695329v1

____

Enhanced #genome #replication activity of pandemic #H1N1 #influenza A virus through PA #mutations

 

ABSTRACT

The 2009 pandemic H1N1 (pH1N1) influenza A virus (IAV) is a reassortant virus with two polymerase components, PA and PB2, originating from avian IAV. Avian IAV polymerase does not function efficiently in mammalian cells without host-adaptive mutations. The mechanism by which pH1N1 replicates in human hosts is not fully elucidated, as pH1N1 does not contain the host-adaptive PB2 E627K mutation required for species-specific interaction with ANP32, which facilitates replicase (polymerase oligomer) formation. Our previous research revealed that mutations in PA played a key role in mammalian host adaptation of pH1N1. These mutations were found in two separate domains of PA, the C-terminal (CTD) and N-terminal domains (NTD). We reported that the NTD mutations increase the expression of NP through enhanced association of GRSF1 with the mRNA transcripts. However, the role of CTD mutations, which are located at the interface of the polymerase oligomers, has not been elucidated. In this study, we characterized the effect of key CTD mutations and found that the CTD mutations enhanced genome replication activity and replicase formation in vitro. Unexpectedly, rescued viruses containing only the CTD mutations that enhance genome replication activity had an attenuated viral growth phenotype. However, the introduction of an additional NTD mutation to the virus restored virus growth in mammalian cells. These results suggest that the mutations found in the PA NTD are required together with CTD mutations for balanced genome replication and growth in human cells.

Source: 

Link: https://journals.asm.org/doi/full/10.1128/jvi.01391-25?af=R

____

#Influenza D Virus in Black #Donkeys, Northern #China

 

Abstract

Influenza D virus (IDV) is prevalent in cattle in China, and a risk for spillover to other species exists. We detected IDV antibodies in 6/315 of black donkeys in northern China, suggesting cattle-to-donkey transmission and demonstrating the expanding host range of IDV and the need for reassessment of cross-species transmission risks.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/31/12/25-0666_article

____

Highly Pathogenic Avian #Influenza #H5N1 Clade 2.3.4.4b Virus #Infection in Poultry Farm #Workers, #Washington, #USA, 2024

 

Abstract

Poultry workers in Washington, USA, were infected with highly pathogenic avian influenza A(H5N1) virus and recovered. The viruses were clade 2.3.4.4b genotype D1.1, closely related to viruses causing poultry outbreaks. Continued surveillance and testing for influenza A(H5) clade 2.3.4.4b viruses remain essential for risk assessment and pandemic preparedness of zoonotic influenza viruses.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/31/12/25-1118_article

____

#China, three additional #human cases of #infection with #H9N2 avian #influenza virus (HK CHP, Dec. 23 '25)

{Excerpt} 

Avian influenza A(H9N2): 

-- Guangdong Province: 

1) An individual with onset in November 2025. 

-- Guangxi Zhuang Autonomous Region: 

2) An individual with onset in November 2025. 

-- Hubei Province: 

3) An individual with onset in November 2025. 

(...)

Source: 

Link: https://www.chp.gov.hk/files/pdf/2025_avian_influenza_report_vol21_wk51.pdf

____

#Zoonotic and #Avian #Pathogen Detections in Fecal and Sediment #Samples - A Low-risk, High-throughput One Health Approach to #Surveillance

 

Abstract

Many pathogens, both those with human spillover potential as well as avian-specific viruses, are maintained in wild bird populations. While much surveillance for influenza A viruses (IAVs) is performed annually, surveillance for other pathogens is limited. Sampling of wild birds is often time-consuming, labour-intensive, involves physically handling wild birds, often limited in sample size, and involves handling of potentially infected birds, posing an increased risk of direct exposure for personnel. Given this, additional methods for surveillance are needed. Longitudinal, bi-weekly fecal and sediment sampling was performed at various sites in southern Manitoba, Canada, particularly focused in Winnipeg from May - October 2025. Sites were chosen based on the suitability of the area for waterfowl habitat, the presence of waterfowl in the area, as well as sites in proximity to reported outbreaks of H5N1 influenza virus. Fecal and sediment samples were collected and screened for the presence of influenza A virus (IAV), Newcastle disease virus (NDV), avian reovirus (ARV), and avian poxvirus (APXV). In total, 782 combined fecal and sediment samples were collected. Of the 714 fecal samples, 34 tested positive for IAV (4.8% prevalence). None of the IAV-positive fecal samples tested positive for H5 RNA. Of the 68 sediments tested, 15 tested positive for IAV (22.1% prevalence), four of which further tested positive for H5 RNA. NDV positivity was low, with only four positive fecal samples (0.56% prevalence) that were all collected on the same day. ARV positivity was also low, with five positive sediment samples (7.4% prevalence in sediment samples). Of the 782 total samples collected, of 559 samples that have been tested for APXV to date, all have tested negative. This work expands upon previous work showing the utility of environmental sampling for a variety of avian and zoonotic pathogens using a One Health approach that is both high-throughput and low-risk.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Canadian Institutes of Health Research, Tier 2 Canada Research Chair, 950 231498

Natural Sciences and Engineering Research Council, RGPIN-2018-06036

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.19.694637v1

____

The spatial and temporal #spread of highly pathogenic avian #influenza in North #America: Newton's Cradle hypothesis

 

Abstract

The recent emergence of highly pathogenic H5N1- especially clade 2.3.4.4b has led to widespread mortality in poultry and wild birds and has raised significant concerns for the dairy industry and human health. Migratory waterfowl are considered the main source of infection, and we used publicly available surveillance data and bird observation data from continental North America to show clear seasonal signals correlated with waterfowl movement, both on the continental scale and in three of the four flyways. In early 2024, the virus expanded its host range, and we observed a phase transition with the loss of the seasonal signal coupled with a concomitant increase in the proportion of mammalian cases. We also identified a second harmonic, with a regional east-to-west movement with infections spreading between regional flyways, followed by local viral amplification. We likened this to the movement of balls in a Newton's Cradle with an analogy between potential and viral energy. We used bird data to identify bird species associated with viral cases and identified specific waterfowl species and highlighted the importance of predatory and scavenging birds, specifically raptors and gulls, in local amplification. These findings will help to focus surveillance strategies both at local and regional levels.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

United States Department of Agriculture, AP23OA000000C025

Center for Poultry and Livestock Excellence, CPLE23-11

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.19.695483v1

____

Digest: #Reassortment-based #evolution of #H1N1 subtype Swine #Influenza Virus in #China

 

Abstract

In a new study, Zhao et al. (2025) obtain 959 whole genome sequences of H1N1 subtype swine influenza virus (SIV) isolated from China. Their analysis of the sequences, isolated between 1977 and 2020, reveals how H1N1 lineages have co-evolved and contributed to instances of zoonotic transmission within the region. This study’s findings characterize the long-term evolutionary effects of frequent viral reassortment in SIV and highlight its potential to drive future pandemics.

Source: 

Link: https://academic.oup.com/evolut/advance-article/doi/10.1093/evolut/qpaf262/8400336

____

#Mpox - Multi-country external #situation #report no. 61, published 22 December 2025 (#WHO, summary)

{Summary}

Highlights   

• All clades of monkeypox virus (MPXV) continue to circulate. 

- Unless mpox outbreaks are rapidly contained and human-to-human transmission is interrupted, there is a risk of sustained community transmission.  

• In November 2025, 48 countries across all WHO regions reported a total of 2150 new confirmed mpox cases, including five deaths (case fatality ratio [CFR] 0.2%). 

- About 68% of these cases were reported in the African Region. 

- Four regions observed a decline in confirmed cases in November, compared to October 2025, while the European and Western Pacific regions reported more cases than the previous month.     

• Nineteen countries in Africa reported active transmission of mpox in the last six weeks (2 November– 14 December 2025), with 1435 confirmed cases, including seven deaths (CFR 0.5%). 

- Countries reporting the highest number of cases in this period are the Democratic Republic of the Congo, Guinea, Liberia, Kenya and Ghana; while case reports in Liberia still show indications of a rise, weekly case counts in the other countries have been declining in recent weeks. 

• Romania has reported detection of clade Ib MPXV for the first time, in a case confirmed in August 2025.   

• Outside Africa, community transmission of clade Ib MPXV continues in Spain and in the Netherlands. 

• In the Democratic Republic of the Congo, mpox transmission continues across multiple provinces with cocirculation of clades Ia and Ib MPXV, heterogeneous subnational trends and declining access to testing of suspected cases. 

• The United Kingdom of Great Britain and Northern Ireland has reported a new travel-linked case of mpox with detection of a recombinant MPXV strain containing genetic elements of both clade Ib and clade IIb MPXV. The extent of circulation of the recombinant strain remains unknown.  

• WHO assesses the ongoing public health risk to be moderate for men who have sex with men with new or multiple partners, sex workers and others with multiple partners who may be at risk, and low for the general population with no specific risk factors, continues close monitoring of the situation, and emphases the importance of maintaining surveillance and response capacity, including genomic sequencing notably in locations where multiple MPXV strains co-circulate. 

(...)

Source: 

Link: https://www.who.int/publications/m/item/multi-country-outbreak-of-mpox--external-situation-report--61---22-december-2025

____

#Influenza at the #human - #animal #interface - Summary and #risk #assessment, from 6 November to 19 December 2025 (#WHO, edited)

 

Influenza at the human-animal interface 

Summary and risk assessment, from 6 November to 19 December 2025 {1}

-- New human cases {1,2}: 

- From 6 November to 19 December 2025, based on reporting date, the detection of influenza A(H5N1) in one human, A(H5N5) in one human, A(H9N2) in seven humans, and an influenza A(H1N1) variant virus in one human were reported officially. 

- In addition, one human case of infection with an influenza A(H1N2) variant virus was detected. 

-- Circulation of influenza viruses with zoonotic potential in animals: 

- High pathogenicity avian influenza (HPAI) events in poultry and non-poultry animal species continue to be reported to the World Organisation for Animal Health (WOAH).{3} 

- The Food and Agriculture Organization of the United Nations (FAO) also provides a global update on avian influenza viruses with pandemic potential.{4} 

- Additionally, low pathogenicity avian influenza viruses as well as swine influenza viruses continue to circulate in animal populations. 

-- Risk assessment {5}: 

- Sustained human to human transmission has not been reported associated with the above-mentioned human infection events. 

- Based on information available at the time of this risk assessment update, the overall public health risk from currently known influenza A viruses detected at the human-animal interface has not changed and remains low. 

- The occurrence of sustained human-to-human transmission of these viruses is currently considered unlikely. 

- Although human infections with viruses of animal origin are infrequent, they are not unexpected at the human-animal interface.  

-- IHR compliance {6}: 

- This includes any influenza A virus that has demonstrated the capacity to infect a human and its haemagglutinin (HA) gene (or protein) is not a mutated form of those, i.e. A(H1) or A(H3), circulating widely in the human population. 

- Information from these notifications is critical to inform risk assessments for influenza at the human-animal interface.  

Avian influenza viruses in humans 

-- Current situation:  

- Since the last risk assessment of 5 November 2025, one laboratory-confirmed human case of A(H5N1) infection was detected in Cambodia, and one laboratory-confirmed human case of A(H5N5) virus infection was detected in the United States of America. 

A(H5N1), Cambodia 

- On 16 November 2025, Cambodia notified WHO of a confirmed human infection with avian influenza A(H5N1) in a 22-year-old male from Phnom Penh. 

- The case developed symptoms on 10 November 2025, sought medical care at a clinic, and was diagnosed with pneumonia. 

- He was subsequently admitted to the national hospital in Phnom Penh on 13 November. 

- Samples were collected on the same day and tested positive for avian influenza A(H5N1) on 15 November. 

- His condition deteriorated rapidly, and he died the same day.   

- Investigations conducted in the case's hometown in Kampong Cham Province, which he visited between 4 and 6 November, revealed that the case had apparently healthy domestic birds (chickens and ducks) in his house. 

- However, sick and dead poultry had been reported in the village since 15 October. 

- Samples collected from two ducks and one chicken in the village tested positive for influenza A(H5N1). 

- Enhanced public health surveillance was implemented. 

- Among the case’s contacts, one was symptomatic, and all contacts tested negative for influenza A(H5N1).  

- Eighteen human infections with A(H5N1) viruses have been confirmed in Cambodia in 2025 and nine of these have been fatal. 

- All these cases in 2025 had exposure to domestic birds or their environments. 

- In some cases, domestic birds were reported to be sick or dead. 

- Where the information is available, the genetic sequence data from the viruses from the human cases closely matches that from recent local animal viruses and are identified as clade 2.3.2.1e viruses. 

- From the information available thus far on these recent human cases, there is no indication of human-tohuman transmission of the A(H5N1) viruses.  

A(H5N5), United States of America 

- On 15 November 2025, the United States of America (US) notified WHO of a confirmed human infection with influenza A(H5). 

- The patient was an adult with underlying medical conditions residing in Washington State. 

- The patient developed symptoms including fever during the week ending 25 October 2025. 

- During the week ending 8 November 2025, the patient was hospitalized with a serious illness and subsequently died on 21 November.  

- Respiratory specimens collected at the healthcare facility tested positive for influenza A virus by reverse-transcription-polymerase chain reaction (RT-PCR) and were presumptive positive for influenza A(H5) at the laboratory at the University of Washington. 

- The specimens were sent to the Washington State Public Health Laboratory, where influenza A(H5) was confirmed with the US Centers for Disease Control and Prevention (CDC) influenza A(H5) assay. 

- The sample was received at the CDC on 19 November. Sequencing conducted at the University of Washington and at the CDC indicated this was an influenza A(H5N5) virus belonging to the H5 haemagglutinin (HA) clade 2.3.4.4b.  

- Public health investigation revealed that the patient kept backyard poultry and domestic birds. 

- Additional epidemiological investigations were under way at the time of notification and included active monitoring of anyone who was in close contact with the patient.{7,8} 

- This is the first human case of this subtype reported globally. 

- Human infections with A(H5N1), A(H5N2), A(H5N6) and A(H5N8) have been reported previously. 

- A(H5N5) virus infections in animals have been detected and reported. 

- HPAI A(H5) clade 2.3.4.4b A(H5N5) viruses have been detected in North America in wild birds and wild mammals since at least 2023.{9} 

- According to reports received by WOAH, various influenza A(H5) subtypes continue to be detected in wild and domestic birds in Africa, the Americas, Asia and Europe. 

- Infections in non-human mammals are also reported, including in marine and land mammals.{10} 

- A list of bird and mammalian species affected by HPAI A(H5) viruses is maintained by FAO.{11}

-- Risk Assessment for avian influenza A(H5) viruses:  

1. What is the current global public health risk of additional human cases of infection with avian influenza A(H5) viruses?  

- Most human infections so far have been reported in people exposed to A(H5) viruses, for example, through contact with infected poultry or contaminated environments, including live poultry markets, and occasionally infected mammals and contaminated environments. 

- As long as the viruses continue to be detected in animals and related environments humans are exposed to, further human cases associated with such exposures are expected but remain unusual. 

- The impact for public health if additional sporadic cases are detected is minimal. 

- The current overall global public health risk of additional sporadic human cases is low. 

2. What is the likelihood of sustained human-to-human transmission of avian influenza A(H5) viruses related to the events above?  

- No sustained human-to-human transmission has been identified associated with the recent reported human infections with avian influenza A(H5) viruses. 

- There has been no reported human-to-human transmission of A(H5N1) viruses since 2007, although there may be gaps in investigations. 

- In 2007 and the years prior, small clusters of A(H5) virus infections in humans were reported, including some involving health care workers, where limited human-to-human transmission could not be excluded; however, sustained human-to-human transmission was not reported.  

- Current evidence suggests that influenza A(H5) viruses related to these events did not acquire the ability to efficiently transmit between people, therefore sustained human-to-human transmission is thus currently considered unlikely.  

3. What is the likelihood of international spread of avian influenza A(H5) viruses by travellers?  

- Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. 

- If this were to occur, further communitylevel spread is considered unlikely as current evidence suggests these viruses have not acquired the ability to transmit easily among humans.  

A(H9N2), China  

- Since the last risk assessment of 5 November 2025, China notified WHO of four cases of infection with influenza A(H9N2) on 6 November 2025 and three cases on 12 December 2025. 

- All but two cases were in children. 

- Cases were detected in Guangdong (one), Guangxi (three), Henan (one) and Hubei (two) provinces. 

- The cases had onsets of symptoms in September, October and November 2025. 

- Four cases had reported exposure to backyard poultry, two had exposure to live poultry markets and the source of exposure for one case was under investigation at the time of reporting. 

- All cases had mild illness and recovered, except one in an elderly person with underlying conditions who was hospitalized at the time of reporting with severe pneumonia. 

- No further cases were detected among contacts of these cases. 

- A(H9) viruses were detected in environmental samples collected during the investigations around some of the cases. 

-- Risk Assessment for avian influenza A(H9N2):   

- 1. What is the global public health risk of additional human cases of infection with avian influenza A(H9N2) viruses?   

- Most human cases follow exposure to the A(H9N2) virus through contact with infected poultry or contaminated environments. 

- Most human infections of A(H9N2) to date have resulted in mild clinical illness. 

- Since the virus is endemic in poultry in multiple countries in Africa and Asia, further human cases associated with exposure to infected poultry are expected but remain unusual. 

- The impact to public health if additional sporadic cases are detected is minimal. 

- The overall global public health risk of additional sporadic human cases is low.  

2. What is the likelihood of sustained human-to-human transmission of avian influenza A(H9N2) viruses related to this event?   

- At the present time, no sustained human-to-human transmission has been identified associated with the recently reported human infections with A(H9N2) viruses. 

- Current evidence suggests that A(H9N2) viruses from these cases did not acquire the ability of sustained transmission among humans, therefore sustained human-to-human transmission is thus currently considered unlikely.   

3. What is the likelihood of international spread of avian influenza A(H9N2) virus by travellers?   

- Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. 

- If this were to occur, further community level spread is considered unlikely as current evidence suggests the A(H9N2) virus subtype has not acquired the ability to transmit easily among humans.   

Swine influenza viruses in humans 

Influenza A(H1N1)v, China 

- Since the last risk assessment of 5 November 2025, the detection of a Eurasian avian-like swine influenza A(H1N1)v virus in a human was reported from China on 12 December 2025. 

- A 60-year-old male from Yunnan province had onset of mild illness on 2 November 2025, was hospitalized on 6 November and discharged on 10 November. 

- He had reported exposure to backyard pigs. 

Influenza A(H1N2)v, USA 

- A human case of infection with an influenza A(H1N2)v virus was detected in the state of Vermont in an adult who had an onset of symptoms in early October. 

- The individual was briefly hospitalized and has recovered. 

- The investigation conducted by state public health officials was unable to determine the likely source of exposure or if close contacts developed symptoms. 

- According to the report, no human-to-human transmission was identified associated with this case.{12}  

-- Risk Assessment:  

1. What is the public health risk of additional human cases of infection with swine influenza viruses?  

- Swine influenza viruses circulate in swine populations in many regions of the world. 

- Depending on geographic location, the genetic characteristics of these viruses differ. 

- Most human cases are exposed to swine influenza viruses through contact with infected animals or contaminated environments. 

- Human infection tends to result in mild clinical illness in most cases. 

- Since these viruses continue to be detected in swine populations, further human cases are expected. 

- The impact to public health if additional sporadic cases are detected is minimal. 

- The overall risk of additional sporadic human cases is low.  

2. What is the likelihood of sustained human-to-human transmission of swine influenza viruses?   

- No sustained human-to-human transmission was identified associated with the events described above. 

- Current evidence suggests that contemporary swine influenza viruses have not acquired the ability of sustained transmission among humans, therefore sustained human-to-human transmission is thus currently considered unlikely. 

3. What is the likelihood of international spread of swine influenza viruses by travelers?   

- Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. 

- If this were to occur, further community level spread is considered unlikely as current evidence suggests that these viruses have not acquired the ability to transmit easily among humans. 

Overall risk management recommendations: 

-- Surveillance and investigations

• Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of global strategic surveillance in animals and humans to detect virologic, epidemiologic and clinical changes associated with circulating influenza viruses that may affect human (or animal) health. Continued vigilance is needed within affected and neighbouring areas to detect infections in animals and humans. Close collaboration with the animal health and environment sectors is essential to understand the extent of the risk of human exposure and to prevent and control the spread of animal influenza. WHO has published guidance on surveillance for human infections with avian influenza A(H5) viruses. 

• As the extent of influenza virus circulation in animals is not clear, epidemiologic and virologic surveillance and the follow-up of suspected human cases should continue systematically. Guidance on investigation of non-seasonal influenza and other emerging acute respiratory diseases has been published on the WHO website. 

• Countries should increase avian influenza surveillance in: 

- domestic and wild birds,

- enhance surveillance for early detection in cattle populations in countries where HPAI is known to be circulating, 

- include HPAI as a differential diagnosis in non-avian species, including cattle and other livestock populations, with high risk of exposure to HPAI viruses; 

- monitor and investigate cases in non-avian species, including livestock, report cases of HPAI in all animal species, including unusual hosts, to WOAH and other international organizations, 

- share genetic sequences of avian influenza viruses in publicly available databases, 

- implement preventive and early response measures to break the HPAI transmission cycle among animals through movement restrictions of infected livestock holdings and strict biosecurity measures in all holdings, 

- employ good production and hygiene practices when handing animal products, and protect persons in contact with suspected/infected animals.{13} 

- More guidance can be found from WOAH and FAO. 

- When there has been human exposure to a known outbreak of an influenza A virus in domestic poultry, wild birds or other animals – or when there has been an identified human case of infection with such a virus – enhanced surveillance in potentially exposed human populations becomes necessary. 

- Enhanced surveillance should consider the health care seeking behaviour of the population, and could include a range of active and passive health care and/or communitybased approaches, including: 

> enhanced surveillance in local influenza-like illness (ILI)/SARI systems, 

> active screening in hospitals and of groups that may be at higher occupational risk of exposure, and 

> inclusion of other sources such as traditional healers, private practitioners and private diagnostic laboratories. 

• Vigilance for the emergence of novel influenza viruses with pandemic potential should be maintained at all times including during a non-influenza emergency. In the context of the cocirculation of SARS-CoV-2 and influenza viruses, WHO has updated and published practical guidance for integrated surveillance. 

-- Notifying WHO 

• All human infections caused by a new subtype of influenza virus are notifiable under the International Health Regulations (IHR, 2005).{14} State Parties to the IHR (2005) are required to immediately notify WHO of any laboratory-confirmed{15} case of a recent human infection caused by an influenza A virus with the potential to cause a pandemic{16}. Evidence of illness is not required for this report. Evidence of illness is not required for this report. 

• WHO published the case definition for human infections with avian influenza A(H5) virus requiring notification under IHR (2005): https://www.who.int/teams/global-influenzaprogramme/avian-influenza/case-definitions. 

-- Virus sharing and risk assessment 

• It is critical that these influenza viruses from animals or from humans are fully characterized in appropriate animal or human health influenza reference laboratories. Under WHO’s Pandemic Influenza Preparedness (PIP) Framework, Member States are expected to share influenza viruses with pandemic potential on a timely basis{17} with a WHO Collaborating Centre for influenza of GISRS. The viruses are used by the public health laboratories to assess the risk of pandemic influenza and to develop candidate vaccine viruses.  

• The Tool for Influenza Pandemic Risk Assessment (TIPRA) provides an in-depth assessment of risk associated with some zoonotic influenza viruses – notably the likelihood of the virus gaining human-to-human transmissibility, and the impact should the virus gain such transmissibility. TIPRA maps relative risk amongst viruses assessed using multiple elements. The results of TIPRA complement those of the risk assessment provided here, and those of prior TIPRA analyses will be published at http://www.who.int/teams/global-influenza-programme/avian-influenza/toolfor-influenza-pandemic-risk-assessment-(tipra).  

-- Risk reduction 

• Given the observed extent and frequency of avian influenza in poultry, wild birds and some wild and domestic mammals, the public should avoid contact with animals that are sick or dead from unknown causes, including wild animals, and should report dead birds and mammals or request their removal by contacting local wildlife or veterinary authorities.  

• Eggs, poultry meat and other poultry food products should be properly cooked and properly handled during food preparation. Due to the potential health risks to consumers, raw milk should be avoided. WHO advises consuming pasteurized milk. If pasteurized milk isn’t available, heating raw milk until it boils makes it safer for consumption. 

• WHO has published practical interim guidance to reduce the risk of infection in people exposed to avian influenza viruses. 

-- Trade and travellers 

• WHO advises that travellers to countries with known outbreaks of animal influenza should avoid farms, contact with animals in live animal markets, entering areas where animals may be slaughtered, or contact with any surfaces that appear to be contaminated with animal excreta. Travelers should also wash their hands often with soap and water. All individuals should follow good food safety and hygiene practices.  

• WHO does not advise special traveller screening at points of entry or restrictions with regards to the current situation of influenza viruses at the human-animal interface. For recommendations on safe trade in animals and related products from countries affected by these influenza viruses, refer to WOAH guidance.  

Links:  

-- WHO Human-Animal Interface web page https://www.who.int/teams/global-influenza-programme/avian-influenza 

-- WHO Influenza (Avian and other zoonotic) fact sheet https://www.who.int/news-room/fact-sheets/detail/influenza-(avian-and-other-zoonotic) 

-- WHO Protocol to investigate non-seasonal influenza and other emerging acute respiratory diseases https://www.who.int/publications/i/item/WHO-WHE-IHM-GIP-2018.2 

-- WHO Public health resource pack for countries experiencing outbreaks of influenza in animals:  https://www.who.int/publications/i/item/9789240076884 

-- Cumulative Number of Confirmed Human Cases of Avian Influenza A(H5N1) Reported to WHO  https://www.who.int/teams/global-influenza-programme/avian-influenza/avian-a-h5n1-virus 

-- Avian Influenza A(H7N9) Information https://www.who.int/teams/global-influenza-programme/avian-influenza/avian-influenza-a-(h7n9)virus 

-- World Organisation of Animal Health (WOAH) web page: Avian Influenza  https://www.woah.org/en/home/ 

-- Food and Agriculture Organization of the United Nations (FAO) webpage: Avian Influenza https://www.fao.org/animal-health/avian-flu-qa/en/ 

-- OFFLU http://www.offlu.org/ 

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{1} This summary and assessment covers information confirmed during this period and may include information received outside of this period. 

{2} For epidemiological and virological features of human infections with animal influenza viruses not reported in this assessment, see the reports on human cases of influenza at the human-animal interface published in the Weekly Epidemiological Record here.  

{3} World Organisation for Animal Health (WOAH). Avian influenza. Global situation. Available at: https://www.woah.org/en/disease/avian-influenza/#ui-id-2. 

{4} Food and Agriculture Organization of the United Nations (FAO). Global Avian Influenza Viruses with Zoonotic Potential situation update. Available at: https://www.fao.org/animal-health/situation-updates/global-aiv-withzoonotic-potential. 

{5} World Health Organization (2012). Rapid risk assessment of acute public health events. World Health Organization. Available at: https://iris.who.int/handle/10665/70810. 

{6} World Health Organization. Case definitions for the 4 diseases requiring notification to WHO in all circumstances under the International Health Regulations (2005). Case definitions for the four diseases requiring notification in all circumstances under the International Health Regulations (2005).   

{7} World Health Organization (5 December 2025). Disease Outbreak News; Avian Influenza A(H5N5)- United States of America. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2025DON590. 

{8} US CDC FluView. Weekly US Influenza Surveillance Report: Key Updates for Week 46, ending November 15, 2025. Available at https://www.cdc.gov/fluview/surveillance/2025-week-46.html. 

{9} Erdelyan CNG, Kandeil A, Signore AV, et al. Multiple transatlantic incursions of highly pathogenic avian influenza clade 2.3.4.4b A(H5N5) virus into North America and spillover to mammals. Cell Rep. 2024 Jul 23;43(7):114479. doi:10.1016/j.celrep.2024.114479. Epub 2024 Jul 13. PMID:39003741; PMCID:PMC11305400. 

{10}  World Organisation for Animal Health (WOAH). Avian influenza. Global situation. Available at: https://www.woah.org/en/disease/avian-influenza/#ui-id-2. 

{11} Food and Agriculture Organization of the United Nations. Global Avian Influenza Viruses with Zoonotic Potential situation update. Available at: https://www.fao.org/animal-health/situation-updates/global-aiv-withzoonotic-potential/bird-species-affected-by-h5nx-hpai/en. 

{12} US CDC FluView. Weekly US Influenza Surveillance Report: Key Updates for Week 46, ending November 15, 2025. Available at https://www.cdc.gov/fluview/surveillance/2025-week-46.html. 

{13} World Organisation for Animal Health. Statement on High Pathogenicity Avian Influenza in Cattle, 6 December 2024. Available at: https://www.woah.org/en/high-pathogenicity-avian-influenza-hpai-in-cattle/. 

{14} World Health Organization. Case definitions for the four diseases requiring notification in all circumstances under the International Health Regulations (2005). 

{15} World Health Organization. Manual for the laboratory diagnosis and virological surveillance of influenza (2011). Available at: https://apps.who.int/iris/handle/10665/44518. 

{16} World Health Organization. Pandemic influenza preparedness framework for the sharing of influenza viruses and access to vaccines and other benefits, 2nd edition. Available at: https://iris.who.int/handle/10665/341850. 

{17} World Health Organization. Operational guidance on sharing influenza viruses with human pandemic potential (IVPP) under the Pandemic Influenza Preparedness (PIP) Framework (2017). Available at: https://apps.who.int/iris/handle/10665/259402. 

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Source: 

Link: https://www.who.int/publications/m/item/influenza-at-the-human-animal-interface-summary-and-assessment--19-december-2025

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