H5N1 Bird Flu

# A(H5) Bird Flu Surveillance and Human Monitoring ## Monitoring for Novel Influenza A virus infections among people, including Influenza A(H5) ### Influenza A(H5) affected backyard flocks and epidemiologically linked human cases 1May 12026Nov. ## Related Pages - [Global Human Cases with Avian Influenza A(H5N1), 1997-2026](https://www.cdc.gov/bird-flu/php/surveillance/chart-epi-curve-ah5n1.html)

# H5N1 avian flu returns to Midwest poultry farms, with multiple turkey operations hit ### **Cambodia reports sixth H5N1 case of 2026** In international news, [Cambodia recorded](https://www.facebook.com/photo?fbid=1537405808416177&set=pcb.1537406031749488) its sixth human H5N1 avian flu case of 2026. Cambodia has had 40 human cases of H5N1 since 2023. The most recent case was a 49-year-old man who remains hospitalized for his infection after testing positive for the virus on September 27. The man worked on a farm and had direct contact with sick poultry. Since 2023, most human H5N1 cases in Cambodia have involved a reassortant (2.3.2.1e) between an older H5N1 clade that has circulated in Cambodia since 2014 and the newer clade 2.3.4.4b virus that is circulating globally.

There were 38 confirmed cases in California from September 2024 to January 2025. The last confirmed human case reported in California was on January 14, 2025.

The patient, a thirteen-year-old British Columbian, suffered severe symptoms including respiratory failure but recovered with intensive care in hospital. ## How we usually monitor influenza In this case of a human H5N1 patient in B.C., sequencing efforts found three mutations of interest. ## What this case revealed Using standard approaches, binding to any receptor was essentially undetectable. In a human case of infection with a virus that usually affects birds, we would normally expect to see the surface protein (hemagglutinin) binding with human receptors. But what we saw in the B.C. case of human infection with H5N1 was a reduced ability not only to bind to human receptors, but also to bird cell receptors, resulting in a low ability to fuse with cell membranes.

# HPAI (H5N1) detected in guinea fowl in Taoyuan City, Taiwan; first detection in Dayuan District since 2018 - As of [06 Sep 2026,](https://cdn.who.int/media/docs/default-source/influenza/h5n1-human-case-cumulative-table/cumulative-number-of-confirmed-human-cases-for-avian-influenza-a(h5n1)-reported-to-who--2003-20261829de76-a683-43fa-9b4c-b2a2872ef528.pdf?sfvrsn=eac338ba_3&download=true) 1003 cumulative confirmed human H5N1 cases had been reported to WHO from 25 countries, of which 479 were fatal (case fatality rate (CFR) of 47.9%). Available evidence suggests that circulating A(H5) viruses have not acquired the ability to efficiently transmit between people; however, the zoonotic threat remains elevated due to the spread of viruses among birds. For Taiwan specifically, the primary near-term risk is further poultry-sector amplification and associated economic loss, with human infection risk concentrated among farm workers, culling teams, and live-poultry market handlers who lack adequate personal protective equipment.

# Avian Influenza (H5N1 Bird Flu) ### Confirmed Human Cases of Bird Flu in Tulare County - **Total Confirmed Cases:** 18 - **Changes from Prior Week's Report:** +0 _Confirmed Case reports updated weekly._ _Human cases are reported following confirmatory testing conducted by the Centers for Disease Control and Prevention (CDC)._