The temporal #sequence of #influenza #H1N1 and #Mycoplasma pneumoniae co-infection causes disease severity in Syrian hamster models

 

Abstract

Introduction: 

Influenza H1N1 virus is one of the most prevalent subtypes among influenza viruses, and co-infection with Mycoplasma pneumoniae (Mp) is frequently documented in clinical respiratory infections. However, the pathological mechanisms underlying the temporal sequence of H1N1-Mp co-infection remain poorly characterized, and relevant animal models are lacking.

Methods: 

In this study, we established a model of influenza H1N1 and Mycoplasma pneumoniae co-infection in Syrian hamsters and infected two pathogens in interval of 72 hours. Clinical manifestations, body temperature, body weight, pathogen loads in nasal, pharyngeal, and anal swabs, as well as blood cytokine profiles were dynamically monitored over 14 days post-infection (dpi). Additionally, tissue pathogen loads, histopathological changes, routine blood parameters, and blood biochemistry indicators were evaluated at 7 and 14 dpi.

Results: 

The results demonstrated that hamsters first infected with H1N1 followed by Mp (F-M group) exhibited significantly more severe histopathological lesions (assessed by HE staining), higher pathogen loads, and dysregulated cytokine responses compared to other infection groups.

Conclusion: 

Our findings highlight the critical role of infection order in determining the severity of H1N1-Mp co-infection, providing novel insights into the temporal dynamics and pathogenic mechanisms of respiratory co-infections.

Source: 

Link: https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2026.1787294/full

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Identification of a Key #Hemagglutinin #Mutation Mediating #Antibody Escape in #Influenza #H1N1pdm09 Viruses

 

Abstract

Background: 

The H1N1 influenza A virus evades host immunity through continuous antigenic drift, posing a significant challenge to broad-spectrum neutralizing antibody therapies. This study aims to systematically evaluate the neutralizing capacity of the broad-spectrum antibody C12H5 against H1N1 strains from different eras and identify key immune escape mutation sites. 

Methods: 

Three representative H1N1 virus strains from 2009, 2018, and 2023 were selected. An antigen–antibody binding prediction model based on the ESM-2 large language model was constructed by integrating 48,762 GISAID sequence data and deep mutation scanning data from the Bloom laboratory. Candidate escape sites were screened using SHAP (SHapley Additive exPlanations) value analysis. Mutant viruses were constructed via reverse genetics, and their neutralizing capacity and replication fitness were validated through hemagglutination inhibition assays, microneutralization assays, and viral growth kinetics analysis. 

Results: 

Machine learning scoring identified five potential escape sites, with K147 exhibiting the highest overall score (0.92). SHAP analysis revealed that the K147 site within the HA protein’s 130-loop region received the highest importance score (0.28), significantly surpassing other candidate sites. Experimental validation revealed that the K147N mutation reduced neutralizing potency against C12H5 by 8-fold (from 1:1024 to 1:128) and approximately 6-fold in microneutralization assays (from 8.3 log2 to 5.7 log2), while exhibiting a replication advantage in MDCK cells. Microneutralization assays further confirmed an approximately 6-fold reduction in neutralization sensitivity. Structural analysis indicated that K147 is located at the periphery of the HA receptor-binding domain, immediately adjacent to the receptor-binding site. 

Conclusions: 

K147N is identified as the critical mutation mediating C12H5 immune escape, and this mutation has emerged in 2023 circulating strains. This study provides important molecular targets and early warning mechanisms for broad-spectrum antibody optimization and influenza vaccine updates.

Source: 

Link: https://www.mdpi.com/1999-4915/18/3/349

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A newly emergent N1 #neuraminidase associated with clade 2.3.4.4b highly pathogenic avian #influenza #H5 viruses in North #America

 

Abstract

We investigated the evolutionary history of the newly emergent neuraminidase (am4N1) associated with the D1.1 and D1.2 genotypes of highly pathogenic avian influenza A(H5N1) viruses in North America. Phylogenetic inference places am4N1 in a sister clade to Eurasian avian, swine, and human A(H1N1)pdm09 viruses and distinct from 1918, pre-2009 human seasonal, and classical swine A(H1N1) lineages. Am4N1 descends from diverse avian N1 genes endemic to the Americas. Phylodynamic analysis indicates a monophyletic am4N1 lineage with numerous introductions of viruses carrying the am4N1 gene likely originating from western Canada into the United States during emergence of the D1.1 and D1.2 genotypes. The lineage has diversified and accumulated deletions in the stalk domain. Despite amino acid divergence, structural modeling shows conserved neuraminidase architecture in the globular head. Given its distinct ancestry and amino acid sequence, further studies are needed to assess cross-reactivity of antibodies from prior human A(H1N1)pdm09 infections.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This study did not receive any external funding.

Source: 

Link: https://www.medrxiv.org/content/10.64898/2026.03.09.26347929v1

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Impaired #host shutoff is a fitness cost associated with #baloxavir marboxil #resistance #mutations in #influenza A virus PA/PA-X nuclease domain

 

Abstract

The polymerase acidic (PA) protein is a subunit of the trimeric influenza A virus (IAV) RNA-dependent RNA polymerase and the target of the anti-influenza drug baloxavir marboxil (BXM). As with other direct-acting antivirals, treatment with BXM can lead to selection of viruses carrying resistance mutations. If these mutations have negligible fitness costs, resistant viruses can spread widely and render existing treatments obsolete. Multiple BXM resistance mutations in the nuclease domain of PA have been identified, with I38T and I38M amino acid substitutions occurring frequently. These mutations have minimal to no effects on viral polymerase activity, virus replication, or transmission. However, for reasons that are not well understood, viruses with BXM resistance substitutions have not been able to compete with parental wild-type strains. The IAV genome segment encoding PA also encodes the host shutoff nuclease PA-X, which shares the endonuclease domain with PA but has a unique C-terminal domain generated by ribosomal frameshifting during translation. Unlike their effects on PA activity, the effects of BXM or the I38T/M substitutions on PA-X function remain uncharacterized. In our work, for the first time, we directly examine the effects of baloxavir and the I38T/M substitutions on PA-X activity and show that baloxavir inhibits PA-X activity in a dose dependent manner. Most importantly, we also demonstrate that the I38T/M mutations significantly impair the host shutoff activity of PA-X proteins from different IAV strains of H1N1, H3N2, and H5N1 subtypes. Our work reveals that the deleterious effects of I38T/M on PA-X function may represent an important barrier to the spread of BXM-resistant viruses.

Source: 

Link: https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1013550

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Research Note: Molecular Characteristics and #Genetic #Evolution of #H1N1 Avian #Influenza Virus from Wild #birds in #Shanghai, #China

 

ABSTRACT

The H1N1 influenza virus is a major pandemic and seasonal pathogen with a broad host range, posing a substantial threat to human health and underscoring the need for continuous surveillance. Wild birds, as natural reservoirs of avian influenza viruses (AIVs), carry H1N1 strains capable of reassorting with other influenza viruses, which can drive pandemic emergence. The global migration of wild birds facilitates the spread of these viruses, and their interactions with poultry increase the risk of cross-species transmission, further amplifying the public health threat. However, knowledge of H1N1 genetic diversity in wild birds remains limited. Database analysis shows 80% of avian-origin H1N1 isolates come from wild birds across over 40 countries, mainly in North America, Europe and Asia. This study characterized the molecular traits and genetic evolution of four H1N1 AIVs isolated from common teal and spot-billed ducks during 2019–2021. Phylogenetic and sequence analyses revealed these viruses cluster into distinct lineages, divergent from mammalian H1N1 strains, with complex genetic origins involving frequent recombination and high diversity. Frequent wild bird–poultry transmission elevates zoonotic risks. Our findings highlight wild birds’ critical role in H1N1 transmission and confirm their role as an H1N1 gene pool, emphasizing the need for sustained monitoring and research.

Source: 

Link: https://doi.org/10.1016/j.psj.2026.106580

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Immune history confers #antibody - and T cell-dependent cross-protection against highly pathogenic avian #influenza #H5N1 viruses

 

ABSTRACT

The outbreak of highly pathogenic avian H5 influenza (HPAI) clade 2.3.4.4b in cattle has spread across the United States. Mice with pre-existing immunity to H1N1 virus or with a live-attenuated influenza vaccine showed protection against a lethal bovine-derived HPAI H5N1 viral challenge. Notably, ferrets with mixed immunity also demonstrated protection against a feline-derived H5N1 virus, independent of cross-reactive neutralization titers, but antibodies to whole virus were observed. To investigate protective factors, we conducted T cell epitope mapping using published H1N1 viral sequences and found high conservation of key T cell epitopes in the bovine HPAI H5N1 strain. Depletion of T cells in mice prior to and during primary H1N1 infection impacted cross-protective antibodies to H5N1 virus, with CD4 depletion increasing mortality and CD8 depletion mildly impacting morbidity upon H5N1 viral challenge. This underscores the need to investigate memory T cell responses alongside antibodies in assessing preexisting cross-protection to HPAI H5N1 viruses.

Source: 

Link: https://journals.asm.org/doi/full/10.1128/jvi.02088-25?af=R

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Genetic Characterization and Evolutionary #Insights of Novel #H1N1 Swine #Influenza Viruses Identified from #Pigs in #Shandong Province, #China

 

Abstract

Influenza A viruses exhibit broad host tropism, infecting multiple species including humans, avian species, and swine. Swine influenza virus (SIV), while primarily circulating in porcine populations, demonstrates zoonotic potential with sporadic human infections. In this investigation, we identified two H1N1 subtype swine influenza A virus strains designated A/swine/China/SD6591/2019(H1N1) (abbreviated SD6591) and A/swine/China/SD6592/2019(H1N1) (abbreviated SD6592) in Shandong Province, China. The GenBank accession numbers of the SD6591 viral gene segments are PV464931-PV464938, and the GenBank accession numbers corresponding to each of the eight SD6592 viral gene segments are PV464939-PV464946. Phylogenetic and recombination analyses suggest potential evolutionary differences between the isolates. SD6591 displayed a unique triple-reassortant genotype: comparative nucleotide homology assessments demonstrated that the PB2, PB1, NP, NA, HA, and NEP genes shared the highest similarity with classical swine-origin H1N1 viruses. In contrast, SD6592 maintained genomic conservation with previously characterized H1N1 swine strains, although neither of these two isolates exhibited significant intrasegmental recombination events. Through comprehensive sequence analysis of these H1N1 SIVs, this study provides preliminary insights into their evolutionary history and underscores the persistent risk of cross-species transmission at the human–swine interface. These findings establish an essential foundation for enhancing national SIV surveillance programs and informing evidence-based prevention strategies against emerging influenza threats.

Source: 

Link: https://www.mdpi.com/1999-4915/18/1/117

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PA-X 122V broadly determines the #host shutoff #activity of #influenza A viruses

 

ABSTRACT

Multiple genes are involved in the pathogenicity of influenza A virus. Our previous study reported two naturally occurring amino acid mutations in the polymerase acidic (PA) protein as crucial determinants of the virulence of Eurasian avian-like H1N1 (EA H1N1) influenza viruses. PA-X, an accessory protein encoded by the PA gene, is thought to play a role in viral pathogenicity and regulation of host immune response, but its specific function remains unclear. In this study, we found that two genetically similar EA H1N1 influenza viruses, A/swine/Liaoning/FX38/2017 (FX38) and A/swine/Liaoning/SY72/2018 (SY72), induced significantly different suppression levels of host protein synthesis. The difference in host shutoff activity induced by PA-X protein was the key factor affecting the inhibition of host gene expression. Loss of PA-X expression significantly reduced its host shutoff activity, thereby enhancing host antiviral immune response. PA-X deficiency had no apparent effect on polymerase activity or replication capacity. We pinpointed a single residue 122V involved in the ability of PA-X to inhibit host gene expression and thereby modulate the host antiviral response. Notably, PA-X 122V was highly conserved among multiple subtypes of influenza A viruses and vital for maintaining the inhibitory effects on the host protein synthesis. Together, these findings demonstrate that the PA-X protein plays a major role in the suppression of host protein synthesis during influenza virus infection and elucidate the molecular mechanism by which the amino acid residue 122V in PA-X facilitates its suppression effects on host innate immune responses.

Source: 

Link: https://journals.asm.org/doi/full/10.1128/mbio.03433-25?af=R

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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

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#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/ 

___

{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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#Replication and #Transmission of #Influenza A Virus in Farmed #Mink

 

Abstract

Farmed mink are frequently exposed to circulating influenza A viruses (IAVs), as confirmed by viral isolation and serological evidence. Previous work reveals that naïve mink serve as susceptible hosts for both avian and human influenza strains, highlighting their potential role in influenza ecology. In this study, we investigated whether farmed mink naturally pre-exposed to H9 retain the capacity to serve as “mixing vessels” for reassorting human and avian IAVs. Our results demonstrate that they remain fully susceptible and permissive to infection by both avian H6N6 and human H1N1 influenza strains. Notably, efficient transmission of these viruses occurred among farmed mink, confirming their potential to sustain viral exchange. These findings indicate that farmed mink represent highly permissive hosts capable of facilitating reassortment between circulating human and avian IAVs. Given this risk, current mink farming practices may substantially increase the likelihood of a pandemic emergence. We therefore urge immediate revision, stringent enhancement, and rigorous enforcement of biosecurity protocols and active surveillance systems in fur farming operations.

Source: 

Link: https://www.mdpi.com/1999-4915/18/1/9

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Seasonal #influenza - #Global #situation (#WHO, Dec. 10 '25, excerpts)

 

10 December 2025

Situation at a glance

Seasonal influenza (‘the flu’) is an acute respiratory infection caused by influenza viruses that circulate globally and year-round. 

It can cause illness ranging from mild to severe, sometimes resulting in hospitalization or death. 

Seasonal influenza activity has increased globally in recent months, with an increased proportion of seasonal influenza A(H3N2) viruses being detected. 

This rise coincides with the onset of winter in the northern hemisphere and an increase in acute respiratory infections caused by influenza and other respiratory viruses typically observed at this time of year. 

Although global activity remains within expected seasonal ranges, early increases and higher activity than typical at this time of year have been observed in some regions. 

Seasonal influenza viruses, including A(H3N2) viruses, continually evolve over time. 

Since August 2025, there has been a rapid increase of A(H3N2) J.2.4.1 alias K subclade viruses detected from several countries based on available genetic sequence data. 

These subclade K viruses have several changes from related A(H3N2) viruses. 

Current epidemiological data do not indicate an increase in disease severity, although this subclade marks a notable evolution in influenza A(H3N2) viruses. 

Early estimates suggest that the influenza vaccine continues to provide protection against hospital attendance in both children and adults, even though its effectiveness against clinical disease during the current season remains uncertain. 

Vaccines remain essential, especially for people at high risk of influenza complications and their care givers. 

Even if there are some genetic differences between the circulating influenza viruses and the strains included in the vaccines, the seasonal influenza vaccine may still provide protection against drifted viruses and the other virus strains included in the vaccine. 

Vaccination is still expected to protect against severe illness and remains one of the most effective public health measures. 

WHO continues to monitor global influenza activity and influenza viruses, supports countries in surveillance capacity and updates guidance as needed.

Description of the situation

Globally, influenza activity has increased since October 2025 with influenza A viruses predominant among the viruses detected globally.

In many northern hemisphere countries, acute respiratory infection levels increase at this time of year. 

These increases are typically caused by seasonal epidemics of respiratory pathogens such as influenza, respiratory syncytial virus (RSV) and other common respiratory viruses. 

The exact timing of the onset, the duration, magnitude and the severity of each epidemic might vary by location, influenced by multiple factors such as type of circulating viruses (including influenza and other respiratory pathogens), relative population immunity and environmental conditions.

In the northern hemisphere, some countries have reported early starts to the influenza season. 

In other countries, influenza activity is starting to increase, but has not yet reached the epidemic threshold.

In the southern hemisphere, some countries have had unusually long seasons compared to previous years, with virus activity remaining higher than usual in recent months.

Global influenza surveillance and monitoring is conducted through the Global Influenza Surveillance and Response System (GISRS), a WHO-coordinated network of over 160 institutions in 131 Member States. 

GISRS is tasked with conducting year-round surveillance and monitoring of influenza viruses and serving as the global alert mechanism for the emergence of novel influenza viruses and other respiratory pathogens with pandemic potential.

In the northern hemisphere temperate and sub-tropical countries, areas and territories, influenza activity was generally low from June to August 2025. 

Activity gradually increased in September and continued to increase through November 2025. Influenza A viruses, especially A(H3N2) viruses, predominated during this period (...).

In the southern hemisphere temperate and sub-tropical countries, areas and territories, influenza activity generally decreased from June 2025 and remained low through August. 

However, a slight increase has been observed since September. 

Influenza A(H1N1)pdm09 viruses predominated in June and July; however, A(H3N2) viruses have predominated since September (...).

In tropical areas, there has been sustained influenza activity from June through November. 

Influenza A(H1N1)pdm09 viruses predominated through July. Since then, the proportion of influenza A(H3N2) viruses among reported detections has increased and has become predominant since the end of September (...).

(...)

Genetic characteristics of recent seasonal influenza viruses

Influenza A(H1N1)pdm09 and influenza B/Victoria lineage viruses continue to circulate in all regions albeit at low levels.

Influenza A(H3N2) viruses

Based on genetic sequence data available in GISAID, a mixture of A(H3N2) haemagglutinin (HA) clades and subclades are currently circulating globally; however, there has been a recent and rapid rise in a particular  subclade of A(H3N2), J.2.4.1 (alias subclade K Nextclade/Nextstrain nomenclature). 

A(H3N2) subclade K viruses have genetically drifted from related J.2.4 viruses and have several amino acid changes in their HA in comparison. 

Detections of subclade K viruses are increasing in many parts of the world, with the exception, to date, of South America. 

Subclade K viruses were particularly evident from August 2025 in Australia and New Zealand and have now been detected in more than 34 countries over the last 6 months.

(...)

Overview of seasonal influenza by WHO Region

African region

Influenza detections in the WHO African Region overall increased in October with influenza A(H3N2) predominant. 

The timing and predominant virus varied by zone. 

In the western part of the region, influenza detections increased in September and October with A(H3N2) predominant since October. 

All seasonal subtypes have been detected continuously in the middle and eastern parts of the region. 

Influenza activity peaked in May 2025 in South Africa with almost exclusively A(H3N2) detections; in recent weeks influenza activity has increased slightly but remained low.

Eastern Mediterranean Region

While influenza activity in the WHO Eastern Mediterranean Region overall increased in October with A(H3N2) viruses predominant, there were variations by zone. 

In countries in the northern part of the region, influenza detections increased in October with influenza A(H1N1)pdm09 predominant and lesser proportions of influenza A(H3N2) and B virus detections reported. 

In the Arabian Peninsula, influenza detections also increased in October but with influenza A(H3N2) viruses predominant.

European Region

As of 21 November 2025, reported rates of influenza-like illness (ILI) and/or acute respiratory infection (ARI) in primary care were at baseline levels for most countries and areas of the WHO European Region. 

However, detections were increasing and regionally pooled test percent positivity in primary care sentinel surveillance rose above 10% in weeks 45 and 46 (ending on 15 November), marking the start of the 2025/26 influenza season for the European Region. 

This was approximately four weeks earlier than the median, but not out of the ordinary, with epidemiological trends similar to those observed in the 2022/23 influenza season.

Influenza activity was variable between countries, with those in the west of the Region generally seeing earlier increases of influenza indicators compared to others. 

Influenza admissions, detections, and percent positivity in hospital surveillance were also increasing from inter-seasonal levels, with a higher proportion aged 65 years or older. 

A majority of influenza detections from sentinel and non-sentinel primary care and hospital surveillance systems were A(H3N2) viruses.

Region of the Americas

During the 2025 southern hemisphere season in the Americas, influenza transmission exceeded the seasonal threshold in mid-March, remaining mostly at low to moderate levels. 

Circulation was driven by influenza A(H1N1)pdm09, reaching a peak positivity of 19%. 

Activity then declined to low levels until the end of August, when an increase in circulation was observed, associated with influenza A(H3N2) in Brazil and Chile. 

As of beginning of November, Chile remains at moderate levels of influenza A(H3N2) transmission, without evidence of increased severity or rises in outpatient consultations. 

As of 4 November 2025, subclade K had not been detected in South America.

In the northern hemisphere countries of the Americas, during week 45 of 2025, seasonal influenza circulation remained low, with influenza A(H1N1)pdm09 predominating in the Caribbean and Central America. 

In North America, influenza activity—although still low—was increasing, mainly driven by influenza A virus detections. 

While most detections in Mexico were influenza A(H1N1)pdm09, a predominance of influenza A(H3N2) has been observed in the United States and Canada, with growing detections of the A(H3N2) subclade K.

South-East Asia Region

Influenza detections in the South-East Asia Region started increasing from June,  peaked in August and since then  have generally remained low with some exceptions. 

During the 2025 till November, the proportion of Influenza A among all influenza viruses tested positive was 66% Influenza A(H3N2) was the predominant sub-type (43%) in transmission followed by A(H1N1)pdm09 (~20%). 

In Thailand, influenza detections of predominantly A(H3N2) increased in October and November. 

Influenza A(H3N2) detections also increased since July in Bangladesh and October in Sri Lanka. 

While the region has seen an increase in Influenza A(H3N2), 22 sequences of   subclade K have   been reported in GISAID from Nepal (1), India (4) and Thailand (17) as of 30 November.

Western Pacific Region

Since the beginning of October 2025, influenza seasonal activity has increased in the Western Pacific Region. 

In some countries, including Japan and the Republic of Korea, the onset of the typical seasonal influenza activity period started earlier than in previous years. 

As of 9 November 2025, influenza positivity ranged from 8% to 56% in the northern hemisphere countries. 

In southern hemisphere countries, influenza activity shows mixed trends; positivity has declined in Australia, remains high in New Zealand and is rapidly increasing in Fiji. 

The elevated influenza activity in New Zealand and Fiji is unusual for this time of the year.

The predominant circulating influenza subtype is influenza A(H3N2), marking a shift from A(H1N1)pdm09, which predominated during the 2024-2025 northern hemisphere winter season. 

The increases in influenza have predominantly been driven by the expansion of A(H3N2) subclade K, which represents 89% of sequences submitted to GISAID from the Western Pacific Region (as of 21 November 2025). 

Epidemiology

Seasonal influenza (the flu) is an acute respiratory infection caused by influenza viruses that circulate globally and year-round. In temperate regions, seasonal influenza typically peaks during the winter months, whereas in tropical areas, influenza viruses can circulate year-round with seasonality and intensity that varies across countries.  

There are four types of influenza viruses, types A, B, C and D. Influenza A and B viruses circulate and cause seasonal epidemics of disease:

Influenza A viruses are further classified into subtypes according to the combinations of the proteins on the surface of the virus. Currently circulating in humans are subtype A(H1N1) and A(H3N2) influenza viruses. Influenza B viruses are not classified into subtypes but can be broken down into lineages. Influenza type B viruses belong to either B/Yamagata or B/Victoria lineage.

Influenza spreads easily between people when they cough or sneeze. Influenza disease can cause illness ranging from mild to severe, sometimes resulting in hospitalization or death. While most individuals recover within a week without need for medical care, influenza can lead to serious complication including death, especially among high-risk groups such as young children, the elderly, pregnant women and those with underlying conditions. Health and care workers are at high risk of acquiring influenza virus infection due to increased exposure to the patients, and of further spreading particularly to vulnerable individuals.

Public health response

WHO is enhancing national, regional, and global capacities for influenza preparedness and response, including:

-- continuous global monitoring of influenza viruses and disease activity;

-- issuing seasonal influenza vaccine composition recommendations for both hemispheres;

-- providing technical guidance to Member States on vaccine selection and campaign timing;

-- supporting countries in developing prevention and control strategies;

-- enhancing diagnostic capabilities and laboratory networks;

-- monitoring vaccine effectiveness and susceptibility to approved antivirals;

-- supporting disease surveillance and outbreak response activities;

-- promoting increased vaccine coverage among high-risk groups;

-- facilitating research and development of new therapeutics and countermeasures; and

-- enhancing risk communication for the onset of the influenza season.

WHO risk assessment

Seasonal influenza activity has increased globally in recent months, and influenza A(H3N2) viruses are predominant. 

This rise coincides with the onset of winter in the northern hemisphere. 

Epidemics and outbreaks of seasonal influenza and other circulating respiratory viruses can place significant pressure on healthcare systems.  

Although global activity remains within expected seasonal ranges, early increases and higher activity than typical at this time of year have been observed in some regions. 

Seasonal influenza could place significant pressure on healthcare systems even in non-temperate countries. 

Genetically drifted influenza A(H3N2) viruses, known as subclade K viruses, have been detected in many countries. 

While data on how well the vaccine works against clinical disease this season are still limited, vaccination is still expected to protect against severe illness and remains one of the most effective public health measures. 

WHO advice

Surveillance

Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of year-round global surveillance to detect and monitor virological, epidemiological and clinical changes associated with emerging or circulating influenza viruses that may affect human health and timely virus sharing for risk assessment.  Countries are encouraged to remain vigilant to the threat of influenza viruses and review any unusual epidemiological patterns.

WHO advises Member States to maintain surveillance for respiratory pathogens through an integrated approach, considering country context, priorities, resources and capacities. WHO has published guidance on integrated respiratory virus surveillance. WHO has also updated guidance on assessing influenza epidemic and pandemic severity, including the impact on healthcare facilities.

Clinical management and prophylaxis

Clinical care for seasonal influenza focuses on identifying illness severity, assessing risk of progression, and linking to definitive care. Most cases are mild and self-limiting, but severe disease, marked by respiratory distress, sepsis, acute respiratory distress syndrome or multi-organ failure, requires urgent supportive care and often hospitalization. Clinical management of influenza involves high-quality supportive care—oxygen therapy, monitoring, hydration and respiratory support—and is foundational to improving outcomes, especially in severe cases.

Diagnostic testing should support rapid decision-making: nucleic acid amplification test (NAAT) is conditionally recommended for confirmation of suspected disease in severely unwell patients, while either NAAT or digital immunoassay may be used for non-severe cases, depending on context and resource availability. Testing should be performed early with the aim of identifying people in need of treatment and linking them to care, including antivirals where indicated.

Patients at high risk of progressing to severe disease are likely to benefit from antiviral to reduce their chance of admission to hospital. High-risk groups include adults ≥65 years, those with immunocompromising conditions, chronic cardiovascular, neurological or respiratory disease; malignancy, pregnancy and diabetes further elevate risk. Individuals ≥85 years or those with multiple risk factors are considered extremely high risk and might be considered for antiviral prophylaxis if exposed to influenza.

Infection prevention and control measures in health-care settings

Seasonal influenza is known to cause health care-associated infection outbreaks, in particular in long-term care facilities. WHO advises the use of syndromic screening at all entry points to health-care settings and as part of daily inpatient assessment to ensure that patients with suspected or confirmed infections that are transmissible in health-care settings, including influenza, are identified as soon as possible and that appropriate transmission-based precautions are implemented. WHO advises the use of droplet precautions when caring for patients with suspected or confirmed influenza. This includes appropriate patient placement (isolation) of suspected or confirmed cases, and the use of a medical mask by all health and care workers and visitors when caring for patients with suspected or confirmed influenza.

Appropriate risk assessment for additional personal protective equipment (e.g. eye protection, filtering facepiece respirators, gown, gloves) should be performed by health and care workers when caring for patients with influenza. 

Increased risk of influenza transmission may occur instances where care activities or patient symptoms are likely to generate splashes or sprays of blood, body fluids, secretions and excretions onto mucosa of eyes, nose or mouth; or if in close contact with a patient with respiratory symptoms (e.g. coughing/sneezing) and sprays of secretions may reach the mucosa of eyes, nose or mouth directly, or indirectly via contaminated hands. When performing an aerosol-generating procedure on patients with suspected or confirmed influenza, patient placement in an airborne infection isolation room as well as airborne and contact precautions with eye protection are advised.

Vaccination

Vaccination is the best way to prevent influenza disease. Safe and effective vaccines have been used for more than 60 years. Influenza viruses are constantly changing, so the composition of the seasonal influenza vaccine is regularly updated to contain viruses that are more related to those circulating. WHO, through the Global Influenza Programme and GISRS, in collaboration with partners, continuously monitors influenza viruses and activity globally and recommends seasonal influenza vaccine compositions in February and September for the following northern and southern hemisphere influenza seasons, respectively.

WHO recommends annual vaccination for high-risk groups, including health and care workers. People should ideally get vaccinated just before the influenza season begins for the most effective coverage, although getting vaccinated at any time during the influenza season can still help prevent flu infections. While the effectiveness of the vaccine may vary across seasons and risk groups, it reduces disease severity and lowers the chance of complications and death. Vaccination is especially important for people at high risk of influenza complications and their caregivers.

Genetic changes or drift can occur in the circulating influenza viruses before or during the influenza season, including during the time between vaccine strain selection and the influenza season. Even if there are some genetic differences between the circulating influenza viruses and the strains that are included in the vaccines, the seasonal influenza vaccine may still provide protection against drifted viruses. Current vaccines include three influenza viruses: influenza A(H1N1)pdm09, influenza A(H3N2) and influenza B/Victoria lineage viruses. Therefore, circulation of a drifted virus does not always result in seasonal influenza vaccines being less effective in offering protection against influenza associated illness.

As of now, it remains unclear how the vaccine will protect against clinical disease during this current season. However, early vaccine effectiveness estimates show the current vaccine is 70 to 75% effective at preventing hospital attendance in children aged 2 to 17 years and 30 to 40% effective in adults.[1],[2]

Public health and social measures in the community

The implementation of appropriate and proportionate public health and social measures (PHSM) is an essential component in the overall response to seasonal influenza epidemics. 

Measures such as performing hand hygiene, respiratory hygiene and cough etiquette as well as voluntary self-isolation and mask wearing of individuals who are symptomatic or have tested positive for influenza viruses can reduce transmission of influenza viruses.  

Countries should consider developing a plan to scale up additional PHSM in the event of high or extraordinarily high epidemics.  

Risk communication and community engagement

Member States should consider to update and strengthen their risk communication and community engagement (RCCE) strategy integrating respiratory viruses. Enhanced risk communication and community engagement approach support empowerment of individuals to make informed decisions, countering misinformation, and community-led protection strategies.

Clear, regular, evidence-based, culturally acceptable and context adapted RCCE approaches are essential for building and maintaining trust with the concerned and affected populations to ensure adoption of interventions, practices and behaviours. For RCCE efforts to be successful, it is vital that national policies for RCCE incorporate community engagement and feedback mechanisms that acknowledge and address contextual challenges faced by different population groups, particularly those made most vulnerable. The integration of RCCE approaches to promote vaccination against influenza is also recommended.

WHO does not recommend any restriction on travel to or trade with the countries named in this report, based on the information available on the current event.  

(...)

Source: 

Link: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON586

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