Isolation of Infectious Highly Pathogenic Avian #Influenza #H5N1 Virus from #Fetal #Bovine Serum, #USA, 2025

 

Abstract

In February 2025, we detected highly pathogenic avian influenza virus A(H5N1) clade 2.3.4.4b virus in a fetal bovine serum lot during routine adventitious agent testing. Sequencing confirmed H5N1 genotype B3.13 virus. We found low viral loads in additional samples from the same lot. Heating at 56°C for 30 minutes completely inactivated the virus.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/32/8/26-0077_article

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#USA, #Wastewater Data for Avian #Influenza #H5 (CDC, July 6 '26)

 

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Time Period: June 21, 2026 - June 27, 2026

    -- A(H5) Detection: 6 site(s) (1.3%)

    -- No Detection: 453 site(s) (98.7%)

    -- No samples: 33 site(s)

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Source: 

Link: https://www.cdc.gov/wastewater/emerging-viruses/h5.html?

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#USA, #Michigan Dept. of Health makes #recommendations on preventing #foodborne illness amid growing #cyclosporiasis #outbreak (July 6 '26)

 

July 04, 2026

    As cyclosporiasis cases continue to rise, with the largest increase occurring in Southeast Michigan, the Michigan Department of Health and Human Services (MDHHS) is providing additional recommendations to help prevent foodborne illness related to fresh produce.  

    As of July 4, 2026, no specific produce grower/supplier, or specific produce type has been identified as the source of the outbreak.

    In Michigan, the number of reported cases has risen to 572 as of Saturday, July 4, up from 170 on Tuesday, June 30. 

    Cases remain the highest in Monroe, Lenawee, Washtenaw, Wayne, Shiawassee, Jackson, Oakland and Livingston counties. 

    MDHHS is working with local health departments and the Michigan Department of Agriculture and Rural Development (MDARD) and will update information as it becomes available.

    Cyclosporiasis is an intestinal illness caused by the Cyclospora parasite. People can become infected by consuming food or water that contains the parasite. 

    Cyclospora infects the small intestine (bowel) and usually causes frequent, watery and explosive diarrhea. 

    The time between being exposed and becoming sick is usually about one week but can range from two days to two weeks or more. 

    Untreated, the illness may last from a few days to more than a month. Symptoms may go away and then return.

    Cyclosporiasis is not usually life-threatening, but dehydration from frequent bouts of diarrhea can cause severe illness, particularly among younger or older people and those who have weakened immune systems.

Previous outbreaks

The following foods have been specifically linked to previous Cyclospora outbreaks in the United States and Canada:

    ° Bagged salad mixes and kits (pre-cut lettuce blends with romaine, iceberg, red cabbage, carrots)

    ° Fresh cilantro (coriander leaves)

    ° Fresh basil

    ° Raspberries

    ° Snow peas

    ° Green onions (scallions)

    

    Given the large and increasing number of cases in Michigan, MDHHS recommends that entities in Southeast Michigan who are preparing, processing, or serving raw produce, including restaurants and other commercial kitchens, take the following steps to reduce risks of exposure:

        ° Lettuce/leafy greens:  

            - buy whole heads of lettuce (rather than prewashed, bagged lettuce or salad mixes), throw away the outer 2–3 layers of leaves and wash the inner leaves under running water. For leafy greens that can be cooked, cooking is the safest option.

        ° Cilantro, basil: 

            - Wash thoroughly under running water, separating the leaves.  Safest when cooked.

        ° Green onions: 

            - Trim the root end and remove the outer layer, wash thoroughly under running water. Safest when cooked.

        ° Raspberries: 

            - Their bumpy surface makes them especially hard to clean; the parasite can hide in the tiny crevices.  Safest when cooked (pies, jams etc.). Consider frozen raspberries as an alternative (freezing may reduce but does not guarantee elimination of the parasite).

        ° Snow peas: 

            - Wash under running water and rub the surface. Safest when cooked.

 

    These recommendations are particularly important for people who have a higher risk of dehydration or weakened immune systems such as patients on chemotherapy, organ transplant recipients, infants and young children and elderly people. 

General Rules to Reduce Your Risk

    ° Cook when you can. Heating food to 158°F (70°C) or higher kills Cyclospora.

    ° Wash all fresh produce under clean running water, even if you plan to peel it.

Reminders about routine food safety practices

    ° Wash hands with soap and water before and after handling or preparing food.

    ° Scrub firm fruits and vegetables, such as melons and cucumbers, with a clean produce brush.

    ° Cut away any damaged or bruised areas on fruits and vegetables before preparing and eating.

    ° Wash and sanitize utensils and surfaces before and after handling food. Wash and sanitize display cases and refrigerators where fresh produce is stored.

    ° Wash and sanitize cutting boards, surfaces and utensils used to prepare, serve or store fresh produce.

    ° Refrigerate cut, peeled or cooked fruits and vegetables as soon as possible. 

If you do become ill

    ° People experiencing gastrointestinal illness, such as sudden and ongoing diarrhea, are encouraged to contact their health care provider and reach out to their local health department. 

    ° Cyclosporiasis is treated with antibiotics along with rest and drinking plenty of fluids to maintain hydration.

Source: 

Link: https://www.michigan.gov/mdhhs/inside-mdhhs/newsroom/2026/07/04/mdhhs-makes-recommendations-on-preventing-foodborne-illness-amid-growing-cyclosporiasis-outbreak

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Clade 2.3.4.4b #H5N1 #influenza virus and #SARS-CoV-2 #seroprevalence among owned and feral #cats in #Philadelphia and surrounding communities

 

Abstract

Clade 2.3.4.4b H5NX influenza viruses have spread widely in birds since 2020. In addition to causing disease in birds, these viruses have infected a variety of mammals, including humans. Clade 2.3.4.4b H5N1 viruses are currently causing an outbreak among dairy cattle in the United States, and it is important to determine if other mammals have been exposed to H5NX viruses. Cats, specifically outdoor and feral cats, frequently predate wild birds. Recent studies have shown that cats living on dairy cattle farms can be infected with H5N1. Here, we completed serological studies to determine if owned and feral cats living in an urban environment in the United States have evidence of past H5N1 exposures. We used multianalyte bead-based assays to measure clade 2.3.4.4b hemagglutinin (HA) antibody levels in serum samples collected in July 2023 to June 2025 from 417 feral and 228 owned cats from the greater Philadelphia area. We also measured antibody levels against a panel of HAs from other human and non-human influenza viruses, and the receptor binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We completed additional H5N1 and SARS-CoV-2 neutralization assays using samples that had detectable antibodies in the multianalyte bead-based assays. One cat (0.16%) was positive for H5 antibodies and twenty cats (3.1%) were positive for SARS-CoV-2 antibodies in both binding and neutralization assays. These data suggest that cats in the Philadelphia area have not been routinely exposed to clade 2.3.4.4b H5N1 viruses but have been more commonly exposed to SARS-CoV-2.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.07.03.736283v1

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#USA, #Outbreak of #cyclosporiasis occurring in #Michigan (Dept. of Health, July 1 '26)

 

July 01, 2026

No cause identified for illnesses at this time; state offers prevention tips

LANSING, Mich. - The Michigan Department of Health and Human Services (MDHHS) and Michigan Department of Agriculture and Rural Development (MDARD), in partnership with several local health departments, are actively investigating a large and growing outbreak of cyclosporiasis, a diarrheal illness.  

    As of Tuesday, June 30, more than 170 cases have been reported in Monroe, Lenawee, Washtenaw, Wayne, Livingston, Shiawassee and Jackson counties in the past nine days. Typically, Michigan only identifies around 50 cyclosporiasis cases per year.  

    “Outbreaks of cyclosporiasis have been occurring across the United States and now here in Michigan,” said Dr. Natasha Bagdasarian, chief medical executive. 

    “Based on the unusual number of cases we have identified in a little over a week, we anticipate additional cases of illness being reported. We recommend Michiganders contact their health care provider if they experience sudden, ongoing diarrhea and reach out to their local health department if additional members of their family are suffering from the same symptoms.” 

    Cyclosporiasis is caused by infection with the parasite Cyclospora cayatenensis, which is commonly found in developing countries and spread by food or water contaminated with feces. In recent years, outbreaks have occurred in the U.S. as a result of eating contaminated fresh produce, especially during the summer months. Cyclosporiasis is not known to spread from person to person. 

    Symptoms occur two to 14 days after exposure and may include: 

        ° Frequent watery diarrhea. 

        ° Loss of appetite and weight. 

        ° Abdominal cramps and bloating. 

        ° Nausea (vomiting is less common). 

        ° Low-grade fever. 

    Individuals experiencing sudden gastrointestinal illness are encouraged to be evaluated by a health care provider. Symptoms of cyclosporiasis can be significantly improved with antibiotic treatment. If untreated, the illness may last for a few days to a month or longer. Providers are urged to consider cyclosporiasis among patients presenting with acute gastrointestinal illness in southeast Michigan. 

    “MDARD is committed to ensuring food safety across the state and is working in partnership with local health departments to identify the source of the outbreak and keep consumers safe,” said Jennifer Bonsky, Director of the Human Food Division at MDARD. 

    “In these moments, it becomes even more important to follow all of the essential food preparation guidelines, such as washing your hands before and after preparing food and washing produce before it is consumed.”  

    To help avoid any illness from cyclospora or other harmful bacteria or organisms, MDARD recommends the following: 

        ° Wash all fruits and vegetables thoroughly under running water before eating, cutting or cooking. 

        ° Scrub firm fruits and vegetables, such as melons and cucumbers, with a clean produce brush. 

        ° Cut away any damaged or bruised areas on fruits and vegetables before preparing and eating. 

        ° Refrigerate cut, peeled or cooked fruits and vegetables as soon as possible. 

    Not all cases identified in the last nine days may be connected to the outbreak and the public health investigation is ongoing. State and local officials are interviewing cases to try and identify a common exposure and prevent additional illness. Individuals diagnosed with cyclosporiasis are encouraged to talk to health department staff investigating these illnesses to help identify a potential cause. 

    Additional information is available at About Cyclosporiasis | Cyclosporiasis | CDC.

Current case county by county as of Tuesday, June 30: 

    ° Monroe: 70 

    ° Lenawee: 33 

    ° Washtenaw: 21  

    ° Wayne: 12 

    ° Jackson: 7 

    ° Shiawassee: 7 

    ° 24 cases in 11 other counties and the City of Detroit.

Age 

    ° Age range: 8 years to 84 years 

    ° Average age: 44.3 years 

    ° Median age: 41 years 

# # #

Source: 

Link: https://www.michigan.gov/mdhhs/inside-mdhhs/newsroom/2026/07/01/cyclosporiasis

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#USA, #Wastewater Data for Avian #Influenza #H5 (US CDC, June 26 '26)

 

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Time Period: June 14, 2026 - June 20, 2026

    -- A(H5) Detection: 4 site(s) (0.9%)

    -- No Detection:  455 site(s) (99.1%)

    -- No samples: 32 site(s)

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Source: 

Link: https://www.cdc.gov/wastewater/emerging-viruses/h5.html?

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#USA, #Wastewater Data for Avian #Influenza #H5 (CDC, June 22 '26)

 

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Time Period: June 07, 2026 - June 13, 2026

    -- A(H5) Detection: 4 site(s) (0.9%)

    -- No Detection: 442 site(s) (99.1%)

    -- No samples: 47 site(s)

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Source: 

Link: https://www.cdc.gov/wastewater/emerging-viruses/h5.html?

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#Genomic #epidemiology of two #travel-associated #pediatric #measles viruses within the B3 Lineage

 

Highlights

    • The Children’s Hospital of Philadelphia (CHOP) detected a B3 MeV case in 2023 and in 2025.

    • Whole-genome amplification of the two CHOP B3 MeV isolates was performed.

    • The CHOP genomes were assessed with a global dataset of all 168 National Center for Biotechnology Information B3 MeV near-full length genomes from 2005-2025.

    • The CHOP isolates form a clade with 39 other isolates from four countries, 36 of which cluster with a 15 single nucleotide polymorphism cutoff.

    • The CHOP clade diverged in 2019, contains the most recently emerged B3 nodes, and shares a private mutation in the phosphoprotein at a codon undergoing positive selection.

Abstract

Background

Children’s Hospital of Philadelphia (CHOP) identified a MeV case in late 2023 and also early 2025, both of which were associated with international travel. Of the 24 MeV genotypes, the B3 and D8 lineages have been the most prevalent globally since 2021. Initial genotyping indicated that the two CHOP isolates belong to the B3 lineage.

Objectives

To inform MeV molecular surveillance, we conducted a genomic epidemiology analysis to situate the CHOP strains within the global genetic landscape of past and present MeV B3 cases.

Study design

We performed whole-genome amplification, genome assembly, and phylogenomics of our two MeV cases. These strains were then analyzed alongside all 168 National Center for Biotechnology Information near-full length MeV B3 genomes using population and evolutionary genetic approaches. This dataset includes strains isolated from 13 countries between 2005 and 2025.

Results

The two CHOP strains form a monophyletic group with 39 other isolates from four countries; 36 clade members form a discrete network connected by a 15 single nucleotide polymorphism (SNP) cutoff. The CHOP clade shares a Q45H phosphoprotein mutation at a codon undergoing diversifying selection, as with a H593R hemagglutinin mutation carried by the 2025 CHOP strain. The CHOP clade likely diverged in 2019 and has a median root-to-tip distance of 0.020 compared to 0.017 for the other B3 strains, consistent with this clade encompassing the most recently divergent nodes.

Conclusions

Our work places the CHOP MeV cases within a diversifying and emergent global clade of the dominating B3 lineage that is a future risk due to ongoing B3 MeV transmission.

Source: 

Link: https://www.sciencedirect.com/science/article/abs/pii/S1386653226000557?dgcid=rss_sd_all

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#Genomic #wastewater #surveillance of seasonal and #zoonotic #influenza A viruses in #California during the 2024-2025 flu season

 

Abstract

Wastewater genomic surveillance provides an opportunity to detect human and animal influenza A virus (IAV). We aimed to implement an IAV genomic surveillance framework agnostic to subtype, which enables recovery of IAV from multiple hosts and estimation of proportions across subtypes. We conducted IAV genomic surveillance in wastewater during the 2024-2025 flu season at multiple sites in California and compared these data with available human clinical IAV sequences and test positivity. We applied a custom whole-genome, multi-host IAV probe enrichment panel and adapted our custom expectation-maximization (EM) algorithm to deconvolute IAV mixtures in wastewater and infer subtype relative abundances. Absolute IAV concentrations were quantified using RT-PCR-based assays. H5N1 wastewater and clinical sequences were further characterized by constructing a whole-genome maximum-likelihood phylogenetic tree. Finally, we performed variant analysis to examine amino acid substitutions detected in wastewater. Our IAV probe enrichment method and EM algorithm successfully enriched all eight segments of three circulating IAV subtypes and accurately estimated subclade relative abundances for mixed IAV samples. Seasonal human H1N1pdm09 and H3N2 were detected throughout the study period from both wastewater and clinical sequencing data, with H1N1 subclades 6B.1A.5a.2a.1 and 6B.1A.5a.2a co-circulating, and H3N2 dominated by subclade 3C.2a1b.2a.2a.3a.1. Wastewater surveillance consistently detected H5N1 clade 2.3.4.4b across three monitored wastewater sites, while clinical H5N1 detections, from anywhere in CA, were sporadic and rare. Whole-genome phylogenetic analysis revealed that wastewater H5N1 sequences clustered with reference sequences associated with dairy cow and avian infections, while all human clinical H5N1 sequences clustered exclusively with reference sequences associated with dairy cow infections. Amino acid substitutions were identified across viral segments, and no mutations associated with mammalian adaptation were observed from wastewater samples.

Competing Interest Statement

The authors have declared no competing interest.

Source: 

Link: https://www.medrxiv.org/content/10.64898/2026.06.10.26355323v1

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#USA, #Wastewater Data for Avian #Influenza #H5 (CDC, June 12 '26)

 

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Time Period: May 31, 2026 - June 06, 2026

    -- A(H5) Detection: 3 site(s) (0.7%)

    -- No Detection: 440 site(s) (99.3%)

    -- No samples: 52 site(s)

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Source: 

Link: https://www.cdc.gov/wastewater/emerging-viruses/h5.html?

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#Assessment of #Risk to the #US #Population from the #Ebola Disease #Outbreak Caused by #Bundibugyo Virus, 2026 (MMWR)

 

Summary

    -- What is already known about this topic?

        ° An outbreak of Bundibugyo virus disease (BVD), a type of Ebola disease, is currently occurring, centered in the Ituri province of the Democratic Republic of the Congo (DRC).

    -- What is added by this report?

        ° CDC assessed the risk posed by this ongoing outbreak to the U.S. population during the next 3 months as low.

    -- What are the implications for public health practice?

        ° Ensuring sufficient public health resources to control the outbreak in DRC will be necessary for maintaining a low risk to the U.S. population. If cases arise in the United States, there is public health capacity to contain and control an outbreak, and CDC guidance for U.S. clinicians and public health practitioners can help prevent the potential spread.

Abstract

On May 15, 2026, the ministries of health in the Democratic Republic of the Congo and Uganda declared outbreaks of Bundibugyo virus disease (BVD), a type of Ebola disease. In response to reports of high numbers of suspected cases and deaths in the affected countries, CDC assessed the risk posed by the BVD outbreak to the U.S. population during the next 3 months. This analysis used a standardized risk assessment approach that included epidemiologic data from the ongoing outbreak and historical data from previous Ebola outbreaks; the overall risk was determined by taking into account independent assessments of the likelihood of infection and the impact of infection. The assessment found that the overall risk to the U.S. population posed by the current BVD outbreak during the next 3 months is low, based on the extremely low likelihood of transmission, despite the high impact that potential infection could have and the resources that would be required to respond to the outbreak. Limitations to this assessment included uncertainties around the epidemiology of BVD as well as the current and future scope and geographic spread of the outbreak. CDC continues to monitor factors that could change this risk assessment.

Source: 

Link: https://www.cdc.gov/mmwr/volumes/75/wr/mm7522e2.htm?s_cid=mm7522e2_e&ACSTrackingID=USCDC_921-DM155686&ACSTrackingLabel=Early%20Release%20%E2%80%93%20Vol.%2075%2C%20June%205%2C%202026&deliveryName=USCDC_921-DM155686

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#USA, #Wastewater Data for Avian #Influenza #H5 (CDC, June 5 '26)

 

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Time Period: May 24, 2026 - May 30, 2026

    -- A(H5) Detection: 6 site(s) (1.4%)

    -- No Detection: 421 site(s) (98.6%)

    -- No samples: 69 site(s)

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(...)

Source: 

Link: https://www.cdc.gov/wastewater/emerging-viruses/h5.html?

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#Influenza at the #human - #animal #interface - #Summary and #risk #assessment, from 1 April to 8 May 2026{1} (#WHO, June 5 '26)

 

New human cases{2}: 

    ° From 1 April to 8 May 2026, based on reporting date, detections of influenza A(H5N1) in three humans, influenza A(H5N6) in one human, influenza A(H9N2) in five humans, and influenza A(H1N2) variant ((H1N2)v) virus in one human were reported officially. 

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. 

    ° At present, these viruses are not thought to be capable of sustained human-to-human transmission, although this could change as they evolve.  

    ° 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 A(H5N1), Bangladesh  

    ° On 23 April 2026, Bangladesh notified WHO of one laboratory-confirmed human case of avian influenza A(H5) infection in a child from Sylhet Division. 

    ° The patient developed fever and cough on 27 March 2026 and was admitted to hospital on 28 March with a clinical diagnosis of measles with bronchopneumonia. 

    ° As part of hospital-based influenza surveillance, a sample was collected on 29 March and received by the Institute of Epidemiology, Disease Control and Research (IEDCR) on 20 April. 

    ° The sample tested positive for influenza A(H5N1) on the same day by real-time reverse transcription polymerase chain reaction (RT-PCR). 

    ° The patient was discharged on 30 March. 

    ° No additional cases were reported among identified contacts. 

    ° Epidemiological investigations identified exposure to household poultry.  

    ° This is the second laboratory-confirmed human case of avian influenza A(H5N1) reported in Bangladesh in 2026. 

A(H5N1), Cambodia 

    ° On 22 April 2026, Cambodia notified WHO of one laboratory-confirmed human case of avian influenza A(H5) infection in a 66-year-old woman with comorbidities from Svay Rieng province. 

    ° The patient developed symptoms on 15 April 2026 and was admitted to district hospital on 16 April and provincial hospital the next day. 

    ° As part of severe acute respiratory infection surveillance, a sample was collected on 17 April and received by the National Institute of Public Health on 21 April. 

    ° The sample tested positive for influenza A(H5N1) on the same day by real-time RT-PCR, and the result was confirmed by Institut Pasteur du Cambodge on 22 April. 

    ° The patient died on 22 April. 

    ° No additional cases were reported among 15 identified contacts. 

    ° Epidemiological investigations identified exposure to sick and dead household chickens prior to illness onset.  

    ° Four human infections with A(H5N1) viruses have been confirmed in Cambodia in 2026, including one fatal case. 

    ° Influenza A(H5N1) viruses continue to be detected in domestic birds in Cambodia in 2026, including in areas where human cases have been detected. 

    ° 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-to-human transmission of the A(H5N1) viruses.   

A(H5N1), India 

    ° On 27 March 2026, India notified WHO of one laboratory-confirmed human case of avian influenza A(H5N1) infection in a child from West Bengal state. 

    ° The patient developed fever and cough and was admitted to hospital on 19 March. 

    ° The patient was discharged on 23 March. 

    ° Laboratory testing at the Indian Council of Medical Research (ICMR) National Institute of Virology in Pune confirmed influenza A(H5N1). 

    ° Genomic sequencing identified the virus as belonging to clade 2.3.2.1a, closely related to strains previously reported from Bangladesh and India in 2025. 

    ° No additional cases were reported among identified contacts. 

    ° Epidemiological investigations identified likely indirect exposure to poultry.  

    ° This is the first laboratory-confirmed human case of avian influenza A(H5N1) reported in India in 2026. 

A(H5N6), China 

    ° On 29 April 2026, China notified WHO of one laboratory-confirmed human case of avian influenza A(H5N6) infection in a 55-year-old female with comorbidities from Chongqing Municipality. 

    ° She had onset of symptoms on 16 April 2026 and was hospitalized on 23 April with severe pneumonia.  

    ° The patient died on 3 May 2026. 

    ° She had slaughtered and prepared poultry prior to onset of symptoms. 

    ° Environmental samples collected from the food preparation tools at the patient’s residence tested positive for influenza A(H5). 

    ° No further cases were detected among contacts of the patient. 

    ° This is the first laboratory-confirmed human case of infection with an A(H5N6) virus detected since 2024. 

    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.{7} 

    A list of bird and mammalian species affected by HPAI A(H5) viruses is maintained by FAO.{8}   

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 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.  

    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  

    ° Between 7 April and 6 May 2026, China notified WHO of five laboratory-confirmed cases of A(H9N2) virus infection. 

    ° The first case had comorbidities and developed severe pneumonia. 

    ° All the cases except the child from Jiangxi had exposure to live bird markets or household birds. 

    ° Samples from environments associated with the likely area of exposure of some of these cases tested positive for A(H9) viruses. 

    ° No further cases were detected among contacts of these 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, additional human cases associated with exposure to infected poultry or contaminated environments are expected but remain unusual. 

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

        ° The overall global public health risk is low.  

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

        ° 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.  

    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(H1N2)v, United States  

    ° On 2 May 2026, the United States notified WHO of a laboratory-confirmed case of A(H1N2)v influenza virus infection in an individual under 18 years of age from Nebraska. 

    ° The patient had onset of mild illness in early April 2026 and has recovered. 

    ° A respiratory specimen collected in mid-April as part of routine surveillance was sent to the US Centers for Disease Control and Prevention (CDC). 

    ° Real-time RT-PCR testing by CDC determined the sample was positive for an influenza A(H1N2)v virus. 

    ° Additional genetic and virologic characterization is currently underway. 

    ° Local public health investigations did not identify direct or indirect exposure to swine. 

    ° One household contact had mild respiratory illness also in early April but no additional cases of A(H1N2)v were identified at the time of reporting.{9} 

    ° This is the first human A(H1N2)v infection detected in the United States in 2026.  

Risk assessment for swine influenza viruses:   

    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 event described above. 

        ° Current evidence suggests that contemporary swine influenza viruses have not acquired the ability of sustained transmission among humans.  

    3. What is the likelihood of international spread of swine influenza 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 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.{10} 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).{11,12} State Parties to the IHR (2005) are required to immediately notify WHO of any laboratory-confirmed{13} case of a recent human infection caused by an influenza A virus with the potential to cause a pandemic{14}. 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{15} 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 risk elements. The results of TIPRA complement those of the risk assessment provided here, and those of prior TIPRA risk assessments are published at http://www.who.int/teams/global-influenza-programme/avianinfluenza/tool-for-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/ 

    WOAH/FAO Network of Expertise on Animal Influenza (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 four diseases requiring notification in all circumstances under the International Health Regulations (2005). Available at: https://www.who.int/publications/m/item/case-definitions-for-the-four-diseases-requiring-notification-towho-in-all-circumstances-under-the-ihr-(2005).  

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

{8} 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. 

{9} US CDC. FluView week 17, 8 May 2026 (https://www.cdc.gov/fluview/surveillance/2026-week-17.html). 

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

{11} World Health Organization. International Health Regulations (2005), as amended through resolutions WHA67.13 (2014), WHA75.12 (2022), and WHA77.17 (2024) (https://apps.who.int/gb/bd/pdf_files/IHR_20142022-2024-en.pdf). 

{12} World Health Organization. Case definitions for the four diseases requiring notification in all circumstances under the International Health Regulations (2005) (https://www.who.int/publications/m/item/casedefinitions-for-the-four-diseases-requiring-notification-to-who-in-all-circumstances-under-the-ihr-(2005)). 

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

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

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

Source: 

Link: https://www.who.int/publications/m/item/influenza-at-the-human-animal-interface-summary-and-assessment--8-may-2026

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