2020–2025 H5N1 outbreak

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{{Legend|#FF0000|Countries that have reported deaths of poultry or wild birds linked to highly pathogenic H5N1 infection as of March 2023}}

{{Legend|#800000|Countries that have reported human cases of highly pathogenic H5N1 infection}}

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File:Formation of the index H5N1 virus bearing the 2.3.4.4b HA gene in 2020.png

Genetic reassortment of several influenza A strains culminates in the emergence of a highly pathogenic H5N1 subtype bearing the clade 2.3.4.4b hemagglutinin (HA) gene.{{Cite web |date=22 May 2024 |title=Genetic and antigenic characteristics of clade 2.3.4.4b A(H5N1) viruses identified in dairy cattle in the United States of America |url=https://www.who.int/publications/m/item/genetic-and-antigenic-characteristics-of-clade-2.3.4.4b-a(h5n1)-viruses-identified-in-dairy-cattle-in-the-united-states-of-america |publisher=World Health Organization |access-date=20 July 2024 |archive-date=20 July 2024 |archive-url=https://web.archive.org/web/20240720182811/https://www.who.int/publications/m/item/genetic-and-antigenic-characteristics-of-clade-2.3.4.4b-a(h5n1)-viruses-identified-in-dairy-cattle-in-the-united-states-of-america |url-status=live }}

In May 2021, H5N1 was detected in wild red foxes in the Netherlands.{{Cite journal |last1=Rijks |first1=Jolianne M. |last2=Hesselink |first2=Hanna |last3=Lollinga |first3=Pim |last4=Wesselman |first4=Renee |last5=Prins |first5=Pier |last6=Weesendorp |first6=Eefke |last7=Engelsma |first7=Marc |last8=Heutink |first8=Rene |last9=Harders |first9=Frank |last10=Kik |first10=Marja |last11=Rozendaal |first11=Harry |last12=van den Kerkhof |first12=Hans |last13=Beerens |first13=Nancy |date=November 2021 |title=Highly Pathogenic Avian Influenza A(H5N1) Virus in Wild Red Foxes, the Netherlands, 2021 |journal=Emerging Infectious Diseases |volume=27 |issue=11 |pages=2960–2 |doi=10.3201/eid2711.211281 |pmc=8544991 |pmid=34670656 }} It was later detected in December in Estonia in wild foxes.{{cite journal |vauthors=((European Food Safety Authority, European Centre for Disease Prevention, Control, European Union Reference Laboratory for Avian Influenza; Adlhoch C, Fusaro A, Gonzales JL, Kuiken T, Marangon S, Niqueux É, Staubach C, Terregino C, Aznar I, Muñoz Guajardo I, Baldinelli F)) |title=Avian influenza overview September – December 2021 |journal=EFSA J |volume=19 |issue=12 |pages=e07108 |date=December 2021 |pmid=34987626 |pmc=8698678 |doi=10.2903/j.efsa.2021.7108 }}

In January 2022, an infection in an eighty-year-old man who raises ducks in England was reported. Also in January, infections were reported from the United States in wild birds. In February, infections were reported from commercial poultry centres in the U.S., and Peru reported infections in sea lions.{{Cite news |last=Collyns |first=Dan |date=21 March 2023 |title=First birds, now mammals: how H5N1 is killing thousands of sea lions in Peru |language=en-GB |work=The Guardian |url=https://www.theguardian.com/environment/2023/mar/21/bird-flu-peru-sea-lions-suffer-death-beach-aoe-h5n1 |access-date=30 March 2023 |issn=0261-3077 |archive-date=1 July 2024 |archive-url=https://web.archive.org/web/20240701004410/https://www.theguardian.com/environment/2023/mar/21/bird-flu-peru-sea-lions-suffer-death-beach-aoe-h5n1 |url-status=live }} The virus continued to spread further, infecting additional species of mammals. In October, a mink farm in northwest Spain was affected. In December, a HPAI H5N1 subtype of clade 2.3.4.4b was found in a captive Asian black bear and in wild and captive birds in a wildlife park in France.{{Cite journal |date=24 April 2024 |title=Highly pathogenic avian influenza A (H5N1) clade 2.3.4.4b virus infection in captive bears (Ursus thibetanus) and in captive and wild birds, France, 2022 |url=https://anses.hal.science/anses-04577858v1/file/Briand_Ger%20J%20Vet%20Res_2024.pdf |journal=German Journal of Veterinary Research |language=en |volume=4 |issue=1 |pages=77–81 |doi=10.51585/gjvr.2024.1.0077 |issn=2703-1322 |access-date=28 April 2024 }}

A human case of H5N1 was reported in the U.S. in April, "though this detection may have been the result of contamination of the nasal passages with the virus rather than actual infection."{{Cite press release |date=28 April 2022 |title=U.S. Case of Human Avian Influenza A(H5) Virus Reported |publisher=Centers for Disease Control and Prevention |language=en-us |url=https://www.cdc.gov/media/releases/2022/s0428-avian-flu.html |access-date=24 February 2023 |archive-date=1 July 2024 |archive-url=https://web.archive.org/web/20240701004414/https://www.cdc.gov/media/releases/2022/s0428-avian-flu.html |url-status=live }} In September, Spain reported a human case; this was followed by a second case in November, in a person who worked at the same poultry farm as the first. Both were asymptomatic.{{Cite web |title=Avian Influenza A (H5N1) – Spain |url=https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON420 |access-date=24 February 2023 |publisher=World Health Organization |language=en |archive-date=23 February 2023 |archive-url=https://web.archive.org/web/20230223215403/https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON420 |url-status=live }} In November, China reported a human case, infected due to contact with poultry. The case died from their infection.

A mass Caspian seal die-off in December 2022, with 700 infected seals found dead along the Caspian Sea coastline of Russia's Dagestan republic, worried researchers regarding the possibility that wild mammal-to-mammal spread had begun.{{Cite news |last=Merrick |first=Jane |date=1 February 2023 |title=Mass death of seals raises fears bird flu is jumping between mammals, threatening new pandemic |url=https://inews.co.uk/news/politics/mass-death-of-seals-raises-fears-bird-flu-is-jumping-between-mammals-threatening-new-pandemic-2121376 |access-date=28 September 2024 |website=inews.co.uk |language=en |archive-date=3 February 2023 |archive-url=https://web.archive.org/web/20230203230815/https://inews.co.uk/news/politics/mass-death-of-seals-raises-fears-bird-flu-is-jumping-between-mammals-threatening-new-pandemic-2121376 |url-status=live }}

H5N1 was first detected in the islands of the Antarctic region in October 2023, via a brown skua on Bird Island, near South Georgia. Within several months, hundreds of elephant seals were found dead, as well as fur seals, kelp gulls and further brown skua.{{cite news |last1=Weston |first1=Phoebe |title=Polar bear dies from bird flu as H5N1 spreads across globe |url=https://www.theguardian.com/environment/2024/jan/02/polar-bear-dies-from-bird-flu-age-of-extinction |access-date=4 January 2024 |work=The Guardian |date=2 January 2024 |archive-url=https://web.archive.org/web/20240104070714/https://www.theguardian.com/environment/2024/jan/02/polar-bear-dies-from-bird-flu-age-of-extinction |archive-date=4 January 2024 }}

In December 2023, conservation officials confirmed that a polar bear had died of H5N1 near Alaska's northernmost city, Utqiagvik.

On 22 May 2023, Brazil declared a 180-day "animal health emergency" in response to eight cases of H5N1 found in wild birds. Although Brazil's major poultry-producing regions are in the country's south and the infections were found in Espirito Santo state and Rio de Janeiro state, Brazil, as the world's largest exporter of chicken meat, created an emergency operations center to plan for and mitigate potential further spread of H5N1.{{cite news |last1=Mano |first1=Ana |title=Brazil declares 180-day animal health emergency amid avian flu cases in wild birds |url=https://www.reuters.com/business/healthcare-pharmaceuticals/brazil-declares-180-day-zoosanitary-emergency-amid-avian-flu-cases-wild-birds-2023-05-22/ |access-date=23 May 2023 |publisher=Reuters |date=22 May 2023 |archive-url=https://web.archive.org/web/20230522232556/https://www.reuters.com/business/healthcare-pharmaceuticals/brazil-declares-180-day-zoosanitary-emergency-amid-avian-flu-cases-wild-birds-2023-05-22/ |archive-date=22 May 2023 }}

On 1 April 2023, a domestic dog in Oshawa tested positive for H5N1.{{Cite news |date=4 April 2023 |title=Domestic dog tests positive for avian influenza in Canada |language=en |publisher=Government of Canada |url=https://www.canada.ca/en/food-inspection-agency/news/2023/04/domestic-dog-tests-positive-for-avian-influenza-in-canada.html |access-date=4 April 2023 |archive-date=4 April 2023 |archive-url=https://web.archive.org/web/20230404203338/https://www.canada.ca/en/food-inspection-agency/news/2023/04/domestic-dog-tests-positive-for-avian-influenza-in-canada.html |url-status=live }}

In February 2023, Cambodia reported the death of a girl due to H5N1 infection after developing symptoms on 16 February.{{Cite web |title=Bird flu death: What will happen next and is there a vaccine? |url=https://www.newscientist.com/article/2361276-bird-flu-death-what-will-happen-next-and-is-there-a-vaccine/ |access-date=24 February 2023 |website=New Scientist |language=en-US |archive-date=24 February 2023 |archive-url=https://web.archive.org/web/20230224173500/https://www.newscientist.com/article/2361276-bird-flu-death-what-will-happen-next-and-is-there-a-vaccine/ |url-status=live }}{{Cite news |date=24 February 2023 |title=Bird flu: 11-year-old girl in Cambodia dies after being infected |language=en-GB |work=The Guardian |url=https://www.theguardian.com/world/2023/feb/24/bird-flu-11-year-old-girl-in-cambodia-dies-after-being-infected |access-date=24 February 2023 |issn=0261-3077 |archive-date=1 July 2024 |archive-url=https://web.archive.org/web/20240701004414/https://www.theguardian.com/world/2023/feb/24/bird-flu-11-year-old-girl-in-cambodia-dies-after-being-infected |url-status=live }} The girl's father also tested positive for the virus. The World Health Organization (WHO) described the situation as "worrying" and urged "heightened vigilance".{{Cite news |last=Rigby |first=Jennifer |date=24 February 2023 |title=Bird flu situation 'worrying'; WHO working with Cambodia |language=en |publisher=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/bird-flu-situation-worrying-who-working-with-cambodia-2023-02-24/ |access-date=24 February 2023 |archive-date=24 February 2023 |archive-url=https://web.archive.org/web/20230224130524/https://www.reuters.com/business/healthcare-pharmaceuticals/bird-flu-situation-worrying-who-working-with-cambodia-2023-02-24/ |url-status=live }}{{Cite news |date=24 February 2023 |title=H5N1: Cambodian girl dies in rare bird flu case |language=en-GB |publisher=BBC News |url=https://www.bbc.com/news/world-asia-64754462 |access-date=24 February 2023 |archive-date=6 August 2023 |archive-url=https://web.archive.org/web/20230806073448/https://www.bbc.com/news/world-asia-64754462 |url-status=live }}{{Cite news |title=An 11-year-old girl has died from bird flu in Cambodia. Here's why the WHO is 'worried' |url=https://www.sbs.com.au/news/article/an-11-year-old-girl-has-died-from-bird-flu-in-cambodia-heres-why-the-who-is-worried/xrsutqu6k |access-date=24 February 2023 |website=SBS News |language=en |archive-date=24 February 2023 |archive-url=https://web.archive.org/web/20230224232126/https://www.sbs.com.au/news/article/an-11-year-old-girl-has-died-from-bird-flu-in-cambodia-heres-why-the-who-is-worried/xrsutqu6k |url-status=live }} Further sequencing determined that at least one of the two cases was from an older H5N1 clade, 2.3.2.1c, which had circulated as a common H5N1 strain in Cambodia for many years, rather than the more recent clade 2.3.4.4b, which had caused mass poultry deaths since 2020. This older clade had jumped to humans in the past yet hadn't previously resulted in any known human-to-human transmission.{{cite news |title=Viruses in Cambodian bird flu cases identified as endemic clade |url=https://www.reuters.com/world/asia-pacific/viruses-cambodian-bird-flu-cases-identified-endemic-clade-2023-02-26/ |access-date=27 February 2023 |publisher=Reuters |date=26 February 2023 |archive-url=https://web.archive.org/web/20230226164710/https://www.reuters.com/world/asia-pacific/viruses-cambodian-bird-flu-cases-identified-endemic-clade-2023-02-26/ |archive-date=26 February 2023 }}

On 1 March 2023, as Taiwan raised its travel alert for Cambodia, the WHO and the U.S. Center for Disease and Control and Prevention (CDC), in concert with Cambodian authorities, determined that both of the individuals had been infected through direct contact with poultry.{{cite news |last1=Strong |first1=Matthew |title=Taiwan raises Cambodia travel alert after human H5N1 cases {{!}} Taiwan News {{!}} 1 March 2023 16:02:00 |url=https://www.taiwannews.com.tw/en/news/4824571 |access-date=3 March 2023 |publisher=Taiwan News |date=1 March 2023 |archive-url=https://web.archive.org/web/20230303000313/https://www.taiwannews.com.tw/en/news/4824571 |archive-date=3 March 2023 }}{{cite news |last1=Cheang |first1=Sopheng |title=Cambodia says recent bird flu cases not spread by humans |url=https://abcnews.go.com/International/wireStory/cambodia-recent-bird-flu-cases-spread-humans-97549557 |access-date=3 March 2023 |publisher=ABC News |date=1 March 2023 |archive-url=https://web.archive.org/web/20230301140618/https://abcnews.go.com/International/wireStory/cambodia-recent-bird-flu-cases-spread-humans-97549557 |archive-date=1 March 2023 }}

On 4 February 2023, a 53-year-old patient was admitted to hospital with severe pneumonia in Jiangsu. Genetic sequencing revealed that the H5N1 avian influenza infected in this case belonged to clade 2.3.4.4b.{{cite web |title=Influenza at the human-animal interface Summary and risk assessment, from 27 January to 3 March 2023 |url=https://cdn.who.int/media/docs/default-source/global-influenza-programme/influenza-at-the-human-animal-interface-summary-and-assessment--from-27-january-to-3-march-2023.pdf |publisher=WHO |access-date=31 December 2024 }} She had a co-infection of H5N1 and SARS-CoV-2.{{cite journal |last1=Jin |first1=Ke |last2=Dai |first2=Zixing |last3=Shi |first3=Ping |last4=Li |first4=Yuwen |last5=Zhu |first5=Chuanlong |title=Severe pneumonia with co-infection of H5N1 and SARS-CoV-2: a case report |journal=BMC Infectious Diseases |date=2 January 2024 |volume=24 |issue=1 |page=31 |doi=10.1186/s12879-023-08901-w |doi-access=free |pmid=38166668 |pmc=10763204 }}

In late February 2023, Argentina confirmed a case of H5N1 in industrial poultry, in the Rio Negro province. Avian product exports were suspended as a result.{{Cite news |date=1 March 2023 |title=Argentina suspends poultry exports as first industrial case of bird flu confirmed |language=en |publisher=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/argentina-suspends-poultry-exports-first-industrial-case-bird-flu-confirmed-2023-03-01/ |access-date=30 March 2023 |archive-date=30 March 2023 |archive-url=https://web.archive.org/web/20230330001731/https://www.reuters.com/business/healthcare-pharmaceuticals/argentina-suspends-poultry-exports-first-industrial-case-bird-flu-confirmed-2023-03-01/ |url-status=live }}

In March 2023, H5N1 was detected in black-necked swan populations in Carlos Anwandter Nature Sanctuary, Chile and Uruguay.{{Cite news |title=Influenza aviar: declaran emergencia zoosanitaria por contagio de cisnes de cuello negro en Valdivia |url=https://www.biobiochile.cl/noticias/nacional/region-de-los-rios/2023/03/25/influenza-aviar-declaran-emergencia-zoosanitaria-por-contagio-de-cisnes-de-cuello-negro-en-valdivia.shtml |last1=Salgado |first1=Daniela |date=25 March 2023 |access-date=25 March 2023 |work=Radio Bío-Bío |last2=López |first2=Carlos |language=Spanish |archive-date=25 March 2023 |archive-url=https://web.archive.org/web/20230325080240/https://www.biobiochile.cl/noticias/nacional/region-de-los-rios/2023/03/25/influenza-aviar-declaran-emergencia-zoosanitaria-por-contagio-de-cisnes-de-cuello-negro-en-valdivia.shtml |url-status=live }}{{Cite news |title=En Uruguay siguen apareciendo casos de gripe aviar |url=https://www.elcomercial.com.ar/24375-en-uruguay-siguen-apareciendo-casos-de-gripe-aviar |date=15 March 2023 |access-date=22 March 2023 |work=Diario El Comercial |language=Spanish |archive-date=25 March 2023 |archive-url=https://web.archive.org/web/20230325143838/https://www.elcomercial.com.ar/24375-en-uruguay-siguen-apareciendo-casos-de-gripe-aviar |url-status=live }} In Uruguay the death of ten swans found in the locality of Estación Tapia was attributed to flu. Previously in Uruguay ten hens had died because of the flu in El Monarca, Montevideo.

In late March 2023, Chile detected H5N1 in a 53-year-old man who had severe symptoms.{{Cite news |date=29 March 2023 |title=Chile detects first case of bird flu in a human |language=en |publisher=Reuters |url=https://www.reuters.com/world/americas/chile-detects-first-case-bird-flu-human-2023-03-29/ |access-date=30 March 2023 |archive-date=16 July 2023 |archive-url=https://web.archive.org/web/20230716151001/https://www.reuters.com/world/americas/chile-detects-first-case-bird-flu-human-2023-03-29/ |url-status=live }} The patient survived but had to stay on a ventilator. The virus was determined to be in the 2.3.4.4b lineage.{{cite web |title=Human Infection with highly pathogenic avian influenza A(H5N1) virus in Chile |website=Avian Influenza (Bird Flu) |date=29 March 2023 |url=https://www.cdc.gov/bird-flu/spotlights/chile-first-case-h5n1-addendum.html |access-date=1 July 2024 |archive-date=1 July 2024 |archive-url=https://web.archive.org/web/20240701004414/https://www.cdc.gov/bird-flu/spotlights/chile-first-case-h5n1-addendum.html |url-status=live }}

In September 2023, Uruguay reported upwards of 400 seals and sea lions found dead of H5N1 on the nation's Atlantic coastline and along the River Plate.{{cite news |title=Bird flu kills 400 seals, sea lions in Uruguay |url=https://phys.org/news/2023-09-bird-flu-sea-lions-uruguay.amp |access-date=3 October 2023 |publisher=phys.org |date=30 September 2023 |archive-url=https://web.archive.org/web/20231003054716/https://phys.org/news/2023-09-bird-flu-sea-lions-uruguay.amp |archive-date=3 October 2023 |language=en }} Between January and October 2023, at least 24,000 South American sea lions died from H5N1 flu, with the outbreak starting on the Pacific coast of Peru, moving down the coast to Chile and then up the Atlantic coast of Argentina.{{Cite journal |last1=Plaza |first1=Pablo I. |last2=Gamarra-Toledo |first2=Víctor |last3=Rodríguez Euguí |first3=Juan |last4=Rosciano |first4=Natalia |last5=Lambertucci |first5=Sergio A. |date=1 May 2024 |title=Pacific and Atlantic sea lion mortality caused by highly pathogenic Avian Influenza A(H5N1) in South America |journal=Travel Medicine and Infectious Disease |volume=59 |pages=102712 |doi=10.1016/j.tmaid.2024.102712 |issn=1477-8939 |doi-access=free |pmid=38461878 }}

An outbreak of H5N1 killed 70% of Southern elephant seal pups born in the 2023 breeding season. In surveyed areas of Península Valdés, Argentina, seal mortality rates reached 96%. In February 2024 it was estimated that the outbreak of H5N1 in South America had killed at least 600,000 wild birds and 50,000 mammals since 2022.

H5N1 was detected in dead birds on the Antarctic mainland for the first time in February 2024.{{cite news |last1=Weston |first1=Phoebe |date=27 February 2024 |title=Scientists confirm first cases of bird flu on mainland Antarctica |url=https://www.theguardian.com/environment/2024/feb/26/scientists-confirm-first-cases-of-bird-flu-on-mainland-antarctica |url-status=live |archive-url=https://web.archive.org/web/20240701004917/https://www.theguardian.com/environment/2024/feb/26/scientists-confirm-first-cases-of-bird-flu-on-mainland-antarctica |archive-date=1 July 2024 |access-date=21 March 2024 |agency=The Guardian }} In February, scientists found H5N1 in 12 Antarctic skua seabirds carcasses on Beak Island. Additional cases have also been found at Hope Bay and on the Devil and Paulet islands. In March, scientists detected the virus in nine Adélie penguins and one Antarctic cormorant.{{Cite news |last=Ansede |first=Manuel |date=9 April 2024 |title=Scientists discover 'massive outbreak' of deadly bird flu in Antarctica |url=https://english.elpais.com/science-tech/2024-04-09/scientists-discover-massive-outbreak-of-deadly-bird-flu-in-antarctica.html |url-status=live |archive-url=https://web.archive.org/web/20240409173711/https://english.elpais.com/science-tech/2024-04-09/scientists-discover-massive-outbreak-of-deadly-bird-flu-in-antarctica.html |archive-date=9 April 2024 |access-date=10 April 2024 |website=El País English |language=en-us }}

In May 2024, H5N1 was detected for the first time in Australia after a human child who had returned to the country from India tested positive. The child was infected with the South Asian 2.3.2.1a clade of H5N1 and had severe symptoms but recovered.{{cite news |date=22 May 2024 |title=First human H5N1 case reported in Australia as another highly pathogenic strain of bird flu detected on Victorian farm |url=https://www.theguardian.com/australia-news/article/2024/may/22/victoria-bird-flu-found-meredith-egg-farm-h5n1 |url-status=live |archive-url=https://web.archive.org/web/20240701004918/https://www.theguardian.com/australia-news/article/2024/may/22/victoria-bird-flu-found-meredith-egg-farm-h5n1 |archive-date=1 July 2024 |access-date=22 May 2024 |agency=The Guardian Australia }}{{cite news |last1=Schnirring |first1=Lisa |date=24 May 2024 |title=Australia's imported H5N1 case linked to South Asian clade |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/australias-imported-h5n1-case-linked-south-asian-clade |url-status=live |archive-url=https://web.archive.org/web/20240701004921/https://www.cidrap.umn.edu/avian-influenza-bird-flu/australias-imported-h5n1-case-linked-south-asian-clade |archive-date=1 July 2024 |access-date=24 May 2024 |publisher=CIDRAP, University of Minnesota }}

On 18 April 2024, H5N1 was detected in ducks in Alappuzha district, Kerala. The District Collector decided to initiate the process of culling domestic birds within a {{convert|1|km|mi}} radius from the center of the outbreak.{{Cite news |date=19 April 2024 |editor-last=Sabarwal |editor-first=Harshit |title=Bird flu outbreak reported in ducks in India's Kerala, authorities urge not to panic |url=https://www.wionews.com/india-news/bird-flu-outbreak-reported-in-ducks-in-indias-kerala-authorities-say-no-need-to-panic-712582 |url-status=live |archive-url=https://web.archive.org/web/20240421203544/https://www.wionews.com/india-news/bird-flu-outbreak-reported-in-ducks-in-indias-kerala-authorities-say-no-need-to-panic-712582 |archive-date=21 April 2024 |access-date=21 April 2024 |website=WIO News }} By 9 May 2024, district officials had culled 60,232 birds in Alappuzha. Farmers were compensated ₹100 per ducklings and chicks, ₹200 per older bird, and ₹5 per egg destroyed.{{Cite news |date=9 May 2024 |title=Bird flu outbreak in Alappuzha, 6777 birds to be culled |url=https://www.onmanorama.com/news/kerala/2024/05/09/bird-flu-outbreak-alappuzha-birds-culled.html |url-status=live |archive-url=https://web.archive.org/web/20240511210334/https://www.onmanorama.com/news/kerala/2024/05/09/bird-flu-outbreak-alappuzha-birds-culled.html |archive-date=11 May 2024 |access-date=11 May 2024 |website=Onmanorama }}

In November 2024, a teenager from the Vancouver region became infected with H5N1 avian influenza from an unknown source. Initially presenting with ocular symptoms, the patient later developed a serious pneumonia, indicating a novel progression of disease.{{cite news |last1=Ledford |first1=Heidi |date=20 November 2024 |title=Why a teenager's bird-flu infection is ringing alarm bells for scientists |url=https://www.nature.com/articles/d41586-024-03805-4 |access-date=21 November 2024 |agency=nature.com }} The virus belongs to the 2.3.4.4b clade which has been circulating among poultry in British Columbia, related to virus carried by wild birds migrating along the Pacific flyway.{{Cite web |date=13 November 2024 |title=Canada's national lab confirms H5N1 in hospitalized teen |publisher=Center for Infectious Disease Research & Policy (CIDRAP), University of Minnesota |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/canadas-national-lab-confirms-h5n1-hospitalized-teen |access-date=22 November 2024 |language=en |archive-date=21 November 2024 |archive-url=https://web.archive.org/web/20241121235449/https://www.cidrap.umn.edu/avian-influenza-bird-flu/canadas-national-lab-confirms-h5n1-hospitalized-teen |url-status=live }}

On 18 May, Chinese authorities confirm 275 cases of bird flu in dead Pallas's gulls and other wild birds in two counties in Qinghai province.{{Cite news |date=18 May 2024 |title=Bird flu found in western China as US combats cattle outbreak |url=https://www.reuters.com/world/china/bird-flu-found-western-china-us-combats-cattle-outbreak-2024-05-18/ |access-date=18 May 2024 |publisher=Reuters }}

A cluster of five human infections of H5N1 occurred in Cambodia in late January and early February; one patient died. All patients had recent contact with sick poultry. Genetic sequencing revealed that they were infected by clade 2.3.2.1c, a different lineage from the 2.3.4.4b clade that is causing global outbreaks.{{cite web |title=First Human Influenza A(H5N1) (Bird Flu) Virus Infections in Cambodia |url=https://www.cdc.gov/flu/avianflu/spotlights/2023-2024/cambodia-human-reported-2024.htm |publisher=Centers for Disease Control and Prevention |language=en-us |date=12 February 2024 |access-date=10 March 2024 |archive-date=10 March 2024 |archive-url=https://web.archive.org/web/20240310051930/https://www.cdc.gov/flu/avianflu/spotlights/2023-2024/cambodia-human-reported-2024.htm |url-status=live }} A person in Vietnam died of H5N1 infection around the same time, clade unknown.{{Cite web |date=4 April 2024 |title=Vietnam confirms H5N1 in man's avian flu death |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/vietnam-confirms-h5n1-mans-avian-flu-death |access-date=4 April 2024 |publisher=CIDRAP, University of Minnesota |language=en |archive-date=3 April 2024 |archive-url=https://web.archive.org/web/20240403035847/https://www.cidrap.umn.edu/avian-influenza-bird-flu/vietnam-confirms-h5n1-mans-avian-flu-death |url-status=live }}

In April 2024, the FAO reported that recent reassortment in the Greater Mekong Subregion has produced viruses that carry internal genes from the 2.3.4.4b lineage but the H5 gene from the older 2.3.2.1c lineage. These viruses have been implicated in human cases.{{cite web |title=Officials warn of H5N1 avian flu reassortant circulating in parts of Asia |publisher=CIDRAP, University of Minnesota |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/officials-warn-h5n1-avian-flu-reassortant-circulating-parts-asia |language=en |date=5 April 2024 |access-date=9 April 2024 |archive-date=9 April 2024 |archive-url=https://web.archive.org/web/20240409000936/https://www.cidrap.umn.edu/avian-influenza-bird-flu/officials-warn-h5n1-avian-flu-reassortant-circulating-parts-asia |url-status=live }}

On 5 April, the Philippines reported a H5N1 outbreak on a poultry farm in Leyte, which killed 4,475 birds. Earlier in the year, the Philippines Department of Agriculture temporarily banned poultry exports from several countries including Japan, Belgium, and France.{{Cite news |date=5 April 2024 |title=Philippines reports H5N1 bird flu outbreak on poultry farm |url=https://www.gmanetwork.com/news/topstories/nation/902707/philippines-reports-h5n1-bird-flu-outbreak-on-poultry-farm/story/ |access-date=4 April 2024 |website=GMA News Online |language=en |archive-date=1 July 2024 |archive-url=https://web.archive.org/web/20240701004416/https://www.gmanetwork.com/news/topstories/nation/902707/philippines-reports-h5n1-bird-flu-outbreak-on-poultry-farm/story/ |url-status=live }}

On 6 July, it was reported that two Cambodian children became sick with H5N1 infections after handling dead chickens.{{cite news |last1=Schnirring |first1=Lisa |title=H5N1 avian flu infects 2 children in Cambodia |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/h5n1-avian-flu-infects-2-children-cambodia |access-date=13 July 2024 |publisher=CIDRAP, University of Minnesota |date=9 July 2024 }}

File:Egg index.webp egg price index]]

The US CDC continues to report "widespread" occurrence in wild birds, "sporadic outbreaks" in poultry flocks, and "sporadic infections" in mammals as of March 2024.{{cite web |title=Avian Influenza Current Situation Summary |url=https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm |publisher=Centers for Disease Control and Prevention |language=en-us |date=7 March 2024 |access-date=10 March 2024 |archive-date=10 March 2024 |archive-url=https://web.archive.org/web/20240310051930/https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm |url-status=dead }} As of 8 March 2024, the United States Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) had recorded around 20 mammal species confirmed as being able to be infected by H5N1.{{cite web |title=2022-2024 Detections of Highly Pathogenic Avian Influenza in Mammals |url=https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/hpai-2022/2022-hpai-mammals |website=aphis.usda.gov |access-date=10 March 2024 |archive-date=30 January 2023 |archive-url=https://web.archive.org/web/20230130195517/https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/hpai-2022/2022-hpai-mammals |url-status=dead }} Also in March 2024, H5N1 was confirmed to have infected farmed goats and cows in the USA.{{cite news |last1=Schnirring |first1=Lisa |title=Sick cows in 2 states test positive for avian flu |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/sick-cows-2-states-test-positive-avian-flu |access-date=26 March 2024 |publisher=CIDRAP, University of Minnesota |date=25 March 2024 |archive-date=25 March 2024 |archive-url=https://web.archive.org/web/20240325213617/https://www.cidrap.umn.edu/avian-influenza-bird-flu/sick-cows-2-states-test-positive-avian-flu |url-status=live }}{{Cite news |last=Johnson |first=Brooks |date=20 March 2024 |title=Baby goats in Minnesota infected with bird flu, concerning officials |url=https://www.startribune.com/goat-bird-flu-minnesota-first-ruminant-avian-influenza-mammals-usda-poultry-biosecurity/600352745/ |url-status=live |archive-url=https://web.archive.org/web/20240320195139/https://www.startribune.com/goat-bird-flu-minnesota-first-ruminant-avian-influenza-mammals-usda-poultry-biosecurity/600352745/ |archive-date=20 March 2024 |access-date=15 April 2024 |website=Star Tribune }}

On 2 April, a dairy worker in Texas became infected, and strong indications of cow-to-cow spread were evident as cow herds in five different states became ill.{{cite news |last1=Schnirring |first1=Lisa |title=Avian flu infects person exposed to sick cows in Texas |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/avian-flu-infects-person-exposed-sick-cows-texas |access-date=2 April 2024 |publisher=CIDRAP, University of Minnesota |date=1 April 2024 |archive-date=1 April 2024 |archive-url=https://web.archive.org/web/20240401210504/https://www.cidrap.umn.edu/avian-influenza-bird-flu/avian-flu-infects-person-exposed-sick-cows-texas |url-status=live }} A few days later, on 4 April, H5N1 was confirmed to have spread to several additional dairy herds in six US states, including Texas, along with Idaho, Kansas, New Mexico, Ohio and Michigan. Scientists deemed these to be either cow-to-cow transmission or spillover from wild birds.{{Cite news |last=Polansek |first=Tom |date=5 April 2024 |title=Bird flu dairy cow outbreak widens in Ohio, Kansas, New Mexico |url=https://www.gmanetwork.com/news/topstories/world/902712/bird-flu-dairy-cow-outbreak-widens-in-ohio-kansas-new-mexico/story/ |access-date=4 April 2024 |website=GMA News Online |language=en |archive-date=4 April 2024 |archive-url=https://web.archive.org/web/20240404232056/https://www.gmanetwork.com/news/topstories/world/902712/bird-flu-dairy-cow-outbreak-widens-in-ohio-kansas-new-mexico/story/ |url-status=live }}{{Cite news |last=Orue |first=Maitane |date=4 April 2024 |title=The Idaho State Department of Agriculture detects HPAI in local dairy operation |url=https://www.kmvt.com/2024/04/04/idaho-state-department-agriculture-detects-hpai-local-dairy-operation/ |access-date=4 April 2024 |publisher=KVMT |language=en |archive-date=4 April 2024 |archive-url=https://web.archive.org/web/20240404011011/https://www.kmvt.com/2024/04/04/idaho-state-department-agriculture-detects-hpai-local-dairy-operation/ |url-status=live }}{{Cite news |last=Thomas |first=Patrick |title=Bird Flu Spreads to Cattle, Raising Fears on Farms |url=https://www.wsj.com/finance/commodities-futures/bird-flu-spreads-to-cattle-raising-fears-on-farms-9293b953 |access-date=4 April 2024 |work=The Wall Street Journal |language=en-US |archive-date=4 April 2024 |archive-url=https://web.archive.org/web/20240404161213/https://www.wsj.com/finance/commodities-futures/bird-flu-spreads-to-cattle-raising-fears-on-farms-9293b953 |url-status=live }} On 11 April, H5N1 was found in dairy cattle herds in North Carolina and South Dakota.{{Cite news |last=Tucker |first=Tom |date=11 April 2024 |title=Avian flu reported in South Dakota cattle herd |url=https://www.wdayradionow.com/news/regional-news/75153-avian-flu-reported-in-south-dakota-cattle-herd |url-status=live |archive-url=https://web.archive.org/web/20240412055614/https://www.wdayradionow.com/news/regional-news/75153-avian-flu-reported-in-south-dakota-cattle-herd |archive-date=12 April 2024 |access-date=12 April 2024 |publisher=WDAY Radio |language=en }}{{Cite web |last1=Munyon |first1=Dana |last2=Thompson |first2=Dr. Beth |date=11 April 2024 |title=Highly Pathogenic Avian Influenza Detected in South Dakota Dairy Herd |url=https://news.sd.gov/news?id=news_kb_article_view&sys_id=8021b3f0876982906093bbf6cebb35a8&spa=1 |url-status=live |archive-url=https://web.archive.org/web/20240412060224/https://news.sd.gov/news?id=news_kb_article_view&sys_id=8021b3f0876982906093bbf6cebb35a8&spa=1 |archive-date=12 April 2024 |access-date=12 April 2024 |website=South Dakota's Citizen Portal (sd.gov) }} On 10 April, researchers found several cases of HPAI H5N1 in animals in New York City, including three Canada geese, a red-tailed hawk, a peregrine falcon, and a chicken.{{Cite news |last=Scripps News Staff |date=10 April 2024 |title=Researchers find bird flu cases among several animals in New York City |url=https://www.turnto23.com/researchers-find-bird-flu-cases-among-several-animals-in-new-york-city |archive-url=https://web.archive.org/web/20240412054448/https://www.turnto23.com/researchers-find-bird-flu-cases-among-several-animals-in-new-york-city |archive-date=12 April 2024 |access-date=12 April 2024 |publisher=KERO-TV |location=Bakersfield, Calif. }}{{Cite news |last=Brennan |first=Martha |date=11 April 2024 |title=Bird flu found in animals in New York City parks |url=https://www.irishstar.com/news/new-york-news/bird-flu-found-animals-new-32567950 |access-date=12 April 2024 |work=Irish Star US |archive-date=12 April 2024 |archive-url=https://web.archive.org/web/20240412054949/https://www.irishstar.com/news/new-york-news/bird-flu-found-animals-new-32567950 |url-status=live }} Scientists have also found cases of H5N1 of clade 2.3.4.4b in common bottlenose dolphins from Florida.{{Cite journal |last1=Murawski |first1=Allison |last2=Fabrizio |first2=Thomas |last3=Ossiboff |first3=Robert |last4=Kackos |first4=Christina |last5=Jeevan |first5=Trushar |last6=Jones |first6=Jeremy C. |last7=Kandeil |first7=Ahmed |last8=Walker |first8=David |last9=Turner |first9=Jasmine C. M. |last10=Patton |first10=Christopher |last11=Govorkova |first11=Elena A. |last12=Hauck |first12=Helena |last13=Mickey |first13=Suzanna |last14=Barbeau |first14=Brittany |last15=Bommineni |first15=Y. Reddy |date=18 April 2024 |title=Highly pathogenic avian influenza A(H5N1) virus in a common bottlenose dolphin (Tursiops truncatus) in Florida |journal=Communications Biology |language=en |volume=7 |issue=1 |page=476 |doi=10.1038/s42003-024-06173-x |issn=2399-3642 |pmc=11026403 |pmid=38637646 }}

On 26 April, the FDA reported the virus had spread to cow herds in nine states, including Colorado, with one in five U.S. commercial milk samples testing positive for traces of bird flu.{{Cite news |date=26 April 2024 |title=Bird flu: one in five US commercial milk samples contain traces, says FDA |url=https://www.reuters.com/world/us/us-fda-says-about-1-5-commercial-milk-samples-tested-positive-bird-flu-traces-2024-04-26/ |access-date=26 April 2024 |publisher=Reuters |archive-date=20 June 2024 |archive-url=https://web.archive.org/web/20240620185515/https://www.reuters.com/world/us/us-fda-says-about-1-5-commercial-milk-samples-tested-positive-bird-flu-traces-2024-04-26/ |url-status=live }}{{Cite news |last=Grewe |first=Lindsey |date=28 April 2024 |title=Bird flu confirmed in Colorado dairy cows |url=https://www.kktv.com/2024/04/28/bird-flu-confirmed-colorado-dairy-cows/ |access-date=28 April 2024 |publisher=KKTV |language=en |archive-date=28 April 2024 |archive-url=https://web.archive.org/web/20240428180616/https://www.kktv.com/2024/04/28/bird-flu-confirmed-colorado-dairy-cows/ |url-status=live }} H5N1 was found to be present at high levels in the mammary glands of affected cows, and cats that consumed unpasteurized milk from symptomatic cows displayed a high mortality rate from a severe systemic influenza infection.{{cite journal |last1=Burrough |first1=Eric |last2=Magstadt |first2=Drew |last3=Main |first3=Rodger |title=Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus Infection in Domestic Dairy Cattle and Cats, United States, 2024 |journal=Emerging Infectious Diseases |date=29 April 2024 |volume=30 |issue=7 |pages=1335–1343 |doi=10.3201/eid3007.240508 |pmid=38683888 |url=https://wwwnc.cdc.gov/eid/article/30/7/24-0508_article |access-date=30 April 2024 |archive-date=29 April 2024 |archive-url=https://web.archive.org/web/20240429235750/https://wwwnc.cdc.gov/eid/article/30/7/24-0508_article |url-status=live |pmc=11210653 }} More than half the cats on one farm died after drinking raw milk from infected cows.{{Cite news |date=30 April 2024 |title=More than half of cats died after drinking raw milk from bird flu-infected cows |publisher=CBS News |url=https://www.cbsnews.com/news/cats-died-after-drinking-milk-bird-flu-infected-cows/ |access-date=1 May 2024 |language=en-US |archive-date=1 May 2024 |archive-url=https://web.archive.org/web/20240501002337/https://www.cbsnews.com/news/cats-died-after-drinking-milk-bird-flu-infected-cows/ |url-status=live }} On 10 May, the Biden administration announced it would provide nearly $200 million to help contain the current outbreak. The US Department of Agriculture pledged $98 million at a split of $28,000 per dairy farm, while the Department of Health and Human Services (HHS) will provide $101 million split between the FDA and the US Centers for Disease Control and Prevention (CDC).{{Cite news |url=https://www.reuters.com/business/healthcare-pharmaceuticals/us-provide-nearly-200-million-contain-bird-flu-spread-dairy-farms-2024-05-10/ |title=US to provide nearly $200 million to contain bird flu spread on dairy farms |date=10 May 2024 |access-date=10 May 2024 |publisher=Reuters |last=Douglas |first=Leah }}

On 16 May, the US Department of Agriculture's National Veterinary Services Laboratories confirmed positive tests for the virus in alpacas on a farm in Idaho, who had to be culled.{{Cite news |last=Goodman |first=Brenda |date=28 May 2024 |title=Alpacas test positive for H5N1 bird flu for the first time |url=https://www.cnn.com/2024/05/28/health/alpacas-h5n1-bird-flu/index.html |access-date=29 May 2024 |publisher=CNN |language=en |archive-date=29 May 2024 |archive-url=https://web.archive.org/web/20240529050512/https://www.cnn.com/2024/05/28/health/alpacas-h5n1-bird-flu/index.html |url-status=live }} On 22 May, a farm worker in Michigan was infected with the bird flu due to their regular exposure to infected dairy cows. The person had mild symptoms and recovered.{{Cite news |url=https://www.nbcnews.com/health/health-news/second-human-case-bird-flu-linked-dairy-cows-found-michigan-rcna153536 |title=Second human case of bird flu linked to dairy cows found in Michigan |date=22 May 2024 |last1=Edwards |first1=Erika |last2=Miller |first2=Sara G. |publisher=NBC News |access-date=23 May 2024 |archive-date=23 May 2024 |archive-url=https://web.archive.org/web/20240523043350/https://www.nbcnews.com/health/health-news/second-human-case-bird-flu-linked-dairy-cows-found-michigan-rcna153536 |url-status=live }} It was shown that H5N1 can persist on milking equipment, which provides a probable transmission route for cow-to-cow and cow-to-human spread.{{cite news |last1=Schnirring |first1=Lisa |title=H5N1 avian flu viruses can persist on milking equipment surfaces |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/h5n1-avian-flu-viruses-can-persist-milking-equipment-surfaces |access-date=24 May 2024 |agency=CIDRAP |publisher=University of Minnesota |date=24 May 2024 |archive-date=23 May 2024 |archive-url=https://web.archive.org/web/20240523230917/https://www.cidrap.umn.edu/avian-influenza-bird-flu/h5n1-avian-flu-viruses-can-persist-milking-equipment-surfaces |url-status=live }} On 30 May, it was announced that a second Michigan farm worker from a different dairy farm had been diagnosed with bird flu after exhibiting respiratory symptoms.{{Cite news |last=Mandavilli |first=Apoorva |title=Bird Flu Has Infected a Third U.S. Farmworker |website=The New York Times |date=30 May 2024 |url=https://www.nytimes.com/2024/05/30/health/bird-flu-infection-farmworker.html |access-date=31 May 2024 |archive-date=31 May 2024 |archive-url=https://web.archive.org/web/20240531003635/https://www.nytimes.com/2024/05/30/health/bird-flu-infection-farmworker.html |url-status=live }}{{Cite news |last=Edwards |first=Erika |title=Third person infected in U.S. bird flu outbreak |publisher=NBC News |date=30 May 2024 |url=https://www.nbcnews.com/health/health-news/cdc-third-person-infected-bird-flu-new-symptom-rcna154697 |access-date=31 May 2024 |archive-date=31 May 2024 |archive-url=https://web.archive.org/web/20240531014134/https://www.nbcnews.com/health/health-news/cdc-third-person-infected-bird-flu-new-symptom-rcna154697 |url-status=live }}

In early June, a flock of 4.2 million egg-laying chickens and a flock of 103,000 turkeys were infected in Iowa.{{Cite web |url=https://iowacapitaldispatch.com/briefs/bird-flu-found-in-second-iowa-flock-in-a-week/ |title=Bird flu found in second Iowa flock in a week |last=Strong |first=Jared |date=3 June 2024 |access-date=3 June 2024 |website=Iowa Capital Dispatch |archive-date=3 June 2024 |archive-url=https://web.archive.org/web/20240603160523/https://iowacapitaldispatch.com/briefs/bird-flu-found-in-second-iowa-flock-in-a-week/ |url-status=live }} It was also that reported that HPAI H5N1 had spread to dairy herds in Iowa,{{Cite news |title=Bird flu infects yet another Sioux County dairy herd |date=25 June 2024 |access-date=27 June 2024 |publisher=Iowa Capital Dispatch |website=The Gazette |url=https://www.thegazette.com/agriculture/bird-flu-infects-yet-another-sioux-county-dairy-herd/ |first=Jack |last=O'Connor |archive-date=27 June 2024 |archive-url=https://web.archive.org/web/20240627185746/https://www.thegazette.com/agriculture/bird-flu-infects-yet-another-sioux-county-dairy-herd/ |url-status=live }} as well as Minnesota, Wyoming and Oklahoma,{{cite web |title=Highly Pathogenic Avian Influenza Detected in Oklahoma Dairy Herd |url=https://ag.ok.gov/highly-pathogenic-avian-influenza-detected-in-oklahoma-dairy-herd/ |website=Animal Health |date=12 July 2024 |publisher=Oklahoma Department of Agriculture |access-date=13 July 2024 }} increasing the number of states with infected dairy herds to thirteen.{{cite news |last1=Polansek |first1=Tom |title=Bird flu reported in Iowa dairy herd, expanding US outbreak in cows |url=https://www.canadiancattlemen.ca/daily/bird-flu-reported-in-iowa-dairy-herd-expanding-us-outbreak-in-cows/ |access-date=5 June 2024 |agency=Canadian Cattlemen |date=5 June 2024 }}{{cite web |last1=Crusan |first1=Michael |title=Amid uptick in poultry detections, Minnesota reports first case of avian influenza in a dairy herd |url=https://www.bah.state.mn.us/news_release/amid-uptick-in-poultry-detections-minnesota-reports-first-case-of-avian-influenza-in-a-dairy-herd/#:~:text=H5N1%20Highly%20Pathogenic%20Avian%20Influenza,cows%20had%20signs%20of%20fever. |publisher=Minnesota Board of Animal Health |access-date=6 June 2024 |archive-date=6 June 2024 |archive-url=https://web.archive.org/web/20240606154439/https://www.bah.state.mn.us/news_release/amid-uptick-in-poultry-detections-minnesota-reports-first-case-of-avian-influenza-in-a-dairy-herd/#:~:text=H5N1%20Highly%20Pathogenic%20Avian%20Influenza,cows%20had%20signs%20of%20fever. |url-status=live }}{{cite news |last1=Beck |first1=Madelyn |title=Bird flu found in Wyoming dairy cows |url=https://wyofile.com/bird-flu-found-in-wyoming-dairy-cows/ |access-date=9 June 2024 |agency=Wyofile |date=7 June 2024 |archive-date=9 June 2024 |archive-url=https://web.archive.org/web/20240609082920/https://wyofile.com/bird-flu-found-in-wyoming-dairy-cows/ |url-status=live }} As of 6 June, infected dairy cows in five states, South Dakota, Michigan, Texas, Ohio, and Colorado, had died from the H5N1 avian flu, with an estimated mortality rate of up to 10%.{{Cite news |url=https://www.theglobeandmail.com/world/article-dairy-cows-infected-with-bird-flu-have-died-in-five-us-states/ |title=Dairy cows infected with avian flu have died in five U.S. states |last1=Douglas |first1=Leah |last2=Polansek |first2=Tom |date=6 June 2024 |website=The Globe and Mail |access-date=6 June 2024 |archive-date=1 July 2024 |archive-url=https://web.archive.org/web/20240701004917/https://www.theglobeandmail.com/world/article-dairy-cows-infected-with-bird-flu-have-died-in-five-us-states/ |url-status=live }} Beginning in late June, the USDA launched voluntary pilot programs to test bulk milk tanks on dairy farms in four states: Kansas, Nebraska, New Mexico, and Texas. Farmers who volunteer for the program were allowed to move their herds across state lines without additional testing if their bulk milk tanks were found negative for H5N1 for three consecutive weeks.{{Cite news |url=https://www.kmuw.org/agriculture/2024-06-26/as-bird-flu-spreads-in-the-u-s-kansas-will-begin-voluntary-testing-of-dairy-farm-milk-tanks |title=As bird flu spreads in the U.S., Kansas will begin voluntary testing of dairy farm milk tanks |first=Jennifer |last=Shutt |date=26 June 2024 |access-date=27 June 2024 |archive-url=https://web.archive.org/web/20240626162506/https://www.kmuw.org/agriculture/2024-06-26/as-bird-flu-spreads-in-the-u-s-kansas-will-begin-voluntary-testing-of-dairy-farm-milk-tanks |archive-date=26 June 2024 |url-status=live |website=KMUW |publisher=KCUR-FM }}

By the end of July, it had become apparent that Weld County, Colorado had become the centre of the unprecedented multi-species outbreak of H5N1 in the United States. Outbreaks in multiple large poultry facilities and intensive dairy farms led to ten human farm-worker cases being reported in and around the county.{{cite news |last1=Schnirring |first1=Lisa |title=Colorado reports 2 more avian flu infections in poultry cullers |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/colorado-reports-2-more-avian-flu-infections-poultry-cullers |access-date=27 July 2024 |publisher=CIDRAP, University of Minnesota |date=26 July 2024 }} Research conducted in this region showed H5N1 as having the ability to replicate copiously in bovine mammary glands leading to multi-directional intra- and inter-species transmission between cows, humans, cats, birds and a raccoon. It was also shown that asymptomatic cows could spread the disease.{{cite journal |last1=Caserta |first1=L.C. |last2=Frye |first2=E.A. |last3=Butt |first3=S.L. |last4=Dimitrov |first4=K.M. |last5=Diel |first5=D.G. |title=Spillover of highly pathogenic avian influenza H5N1 virus to dairy cattle |journal=Nature |date=25 July 2024 |volume=634 |issue=8034 |pages=669–676 |doi=10.1038/s41586-024-07849-4 |doi-access=free |pmid=39053575 |pmc=11485258 |bibcode=2024Natur.634..669C }} In response, the Colorado authorities brought in mandatory milk tank testing (excluding raw milk producers) and an on-line data tracker for human cases in the state.{{cite web |title=Colorado Avian Influenza Updates |url=https://ag.colorado.gov/animal-health/reportable-diseases/avian-influenza/highly-pathogenic-avian-influenza-hpai-outbreak |publisher=Colorado Department of Agriculture |access-date=27 July 2024 }} On 31 July, a study found 2 farmworkers who had not been tested for bird flu had antibodies against it.{{cite news |last1=Maxmen |first1=Amy |last2=KFF Health News |title=Bird Flu Cases in People Are Being Undercounted |url=https://www.scientificamerican.com/article/bird-flu-cases-in-people-are-being-undercounted/ |access-date=18 December 2024 |work=Scientific American |date=1 August 2024 |archive-date=13 December 2024 |archive-url=https://web.archive.org/web/20241213140831/https://www.scientificamerican.com/article/bird-flu-cases-in-people-are-being-undercounted/ |url-status=live }}

On 9 August, the Colorado Department of Public Health reported bird flu in domestic cats, including indoor-only cats.{{cite news |last1=Bartels |first1=Meghan |title=Bird Flu Is Infecting Pet Cats. Here's What You Need to Know |url=https://www.scientificamerican.com/article/bird-flu-is-infecting-pet-cats-heres-what-you-need-to-know/ |access-date=18 December 2024 |work=Scientific American |date=19 August 2024 |archive-date=17 December 2024 |archive-url=https://web.archive.org/web/20241217185149/https://www.scientificamerican.com/article/bird-flu-is-infecting-pet-cats-heres-what-you-need-to-know/ |url-status=live }} In late August, H5N1 had spread to dairy cow herds in California.{{cite news |last1=Polansek |first1=Tom |title=Bird flu infects California dairy cows, widening US outbreak |url=https://www.reuters.com/world/us/us-tests-bird-flu-california-dairy-cattle-2024-08-30/ |access-date=1 September 2024 |publisher=Reuters |date=31 August 2024 }} On 22 August, the first person in the U.S. who didn't work with poultry or dairy cows was hospitalized with the H5 influenza virus. This person is also the 15th human case of H5 reported in the U.S. since 2022.{{cite news |last1=Lovelace Jr. |first1=Berkeley |title=Person infected with bird flu in Missouri had no contact with animals |url=https://www.nbcnews.com/health/health-news/person-infected-bird-flu-missouri-no-contact-animals-know-rcna170010 |access-date=18 December 2024 |publisher=NBC News |date=6 September 2024 }}

In September 2024, the CDC confirms that two dairy workers in California have contracted bird flu, marking the 15th and 16th human cases in this year's ongoing outbreak, which has impacted dairy cows nationwide.{{Cite news |date=3 October 2024 |title=Two California dairy workers were infected with bird flu, latest human cases in US |url=https://apnews.com/article/california-human-bird-flu-h5n1-dairy-worker-aa64a161ccf766e8da73e127b126f580 |access-date=6 October 2024 |publisher=Associated Press |language=en |archive-date=5 October 2024 |archive-url=https://web.archive.org/web/20241005232909/https://apnews.com/article/california-human-bird-flu-h5n1-dairy-worker-aa64a161ccf766e8da73e127b126f580 |url-status=live }} The cases occurred in California's Central Valley, where over 50 herds have been affected since August. Both workers, who had contact with infected cattle, developed mild symptoms, including conjunctivitis. The CDC confirmed the positive test results on Thursday, while state health officials noted that the workers were employed at separate farms, indicating the infections likely resulted from animal exposure rather than human transmission. In October 2024, a third farmworker in California has tested positive for bird flu, according to the state's health department, marking the 17th potential human case of H5N1 in the U.S. since March.{{Cite news |last=Goodman |first=Brenda |date=8 October 2024 |title=As bird flu outbreak expands in California, dairy farms report it's worse than they expected |url=https://us.cnn.com/2024/10/08/health/bird-flu-california-dairy-farms/index.html |access-date=10 October 2024 |publisher=CNN |language=en }} Like the previous two cases, this farmworker had contact with infected dairy cattle, and investigators believe the transmission occurred from animals rather than between people.

By late October, California had reported that 133 of its 1,100 dairy herds were infected, with a bovine mortality rate of around 15%. The business interests of the heavily corporatised dairy and livestock industries being prioritised over public health and animal welfare was stipulated as the main cause of the failure to control the novel outbreak.{{cite news |last1=Eban |first1=Katherine |title=Inside the Bungled Bird Flu Response, Where Profits Collide With Public Health |url=https://www.vanityfair.com/news/story/inside-the-bungled-bird-flu-response |access-date=23 October 2024 |agency=Vanity Fair |date=21 October 2024 |archive-date=6 November 2024 |archive-url=https://web.archive.org/web/20241106034114/https://www.vanityfair.com/news/story/inside-the-bungled-bird-flu-response |url-status=live }} H5N1 was also detected in a pig in Oregon, the first ever reported case in the USA.{{cite news |last1=Douglas |first1=Leah |last2=Polansek |first2=Tom |title=US detects H5N1 bird flu in a pig for the first time |url=https://www.reuters.com/business/healthcare-pharmaceuticals/us-detects-h5n1-bird-flu-swine-first-time-2024-10-30/ |access-date=30 October 2024 |publisher=Reuters |date=30 October 2024 }} Meanwhile, by late November human cases of H5N1 in the USA increased to over fifty for the year with infections being reported in seven states.{{cite news |last1=Stobbe |first1=Mike |last2=Aleccia |first2=JoNel |title=First case of bird flu infection in a U.S. child confirmed in California, officials say |url=https://www.pbs.org/newshour/health/first-case-of-bird-flu-infection-in-a-u-s-child-confirmed-in-california-officials-say |access-date=1 December 2024 |publisher=PBS |date=22 November 2024 |archive-date=29 November 2024 |archive-url=https://web.archive.org/web/20241129143555/https://www.pbs.org/newshour/health/first-case-of-bird-flu-infection-in-a-u-s-child-confirmed-in-california-officials-say |url-status=live }} On 7 November, the CDC reported asymptomatic bird flu infection in 4 workers at dairy farms. The workers didn't recall ever being sick but had antibodies showing that they had been infected with bird flu.{{cite news |last1=Edwards |first1=Erika |last2=Fattah |first2=Mustafa |title=Dairy workers may have bird flu without feeling sick, CDC reports |url=https://www.nbcnews.com/health/health-news/bird-flu-no-symptoms-test-cdc-dairy-rcna179098 |access-date=18 December 2024 |publisher=NBC News |date=7 November 2024 |archive-date=17 December 2024 |archive-url=https://web.archive.org/web/20241217192507/https://www.nbcnews.com/health/health-news/bird-flu-no-symptoms-test-cdc-dairy-rcna179098 |url-status=live }} On 22 November, the CDC confirmed the first case of bird flu in a U.S. child, being the 55th case of bird flu in humans in the U.S. The child also tested positive for other common respiratory viruses.{{cite news |last1=Stobbe |first1=Mike |last2=Aleccia |first2=Jonel |title=California case is the first confirmed bird flu infection in a US child |url=https://apnews.com/article/bird-flu-cdc-6798cd1e2f33067d5b7082b7d34a81a9 |access-date=18 December 2024 |publisher=Associated Press |date=22 November 2024 |archive-date=17 December 2024 |archive-url=https://web.archive.org/web/20241217181951/https://apnews.com/article/bird-flu-cdc-6798cd1e2f33067d5b7082b7d34a81a9 |url-status=live }} New Scientist said that an H5N1 virus infecting a human could acquire all the abilities it needs to become a pandemic virus by swapping genes with a human virus infecting the same individual.{{cite news |last1=Le Page |first1=Michael |title=H5N1 bird flu is closer to gaining pandemic potential than we thought |url=https://www.newscientist.com/article/2459077-h5n1-bird-flu-is-closer-to-gaining-pandemic-potential-than-we-thought/ |access-date=18 December 2024 |work=New Scientist |date=5 December 2024 |archive-date=13 December 2024 |archive-url=https://web.archive.org/web/20241213164859/https://www.newscientist.com/article/2459077-h5n1-bird-flu-is-closer-to-gaining-pandemic-potential-than-we-thought/ |url-status=live }}

On 6 December, the USDA announced a new mandate to test the national milk supply for bird flu as part of efforts to combat the virus's spread among dairy herds. Beginning 16 December, entities handling raw milk, such as dairy processors, would collect and share samples with agricultural officials. The initiative initially targeted six states: California, Colorado, Michigan, Mississippi, Pennsylvania, and Oregon. Since March, over 700 dairy herds, predominantly in California, had already been affected, alongside 57 human cases of mild symptoms reported across the country. The USDA emphasized the program's role in swiftly identifying and controlling outbreaks, ensuring the safety of livestock and public health. The agency further noted that the mandate complemented rather than replaced an earlier April mandate requiring bird flu testing for milk-producing cows before interstate movement.{{cite news |last1=Debusmann Jr |first1=Bernd |title=US orders bird flu testing of national dairy supply |url=https://www.bbc.com/news/articles/c8ewwlgz7k9o |access-date=7 December 2024 |publisher=BBC News |date=6 December 2024 |archive-url=https://web.archive.org/web/20241207061237/https://www.bbc.com/news/articles/c8ewwlgz7k9o |archive-date=7 December 2024 }} On 18 December, Centers for Disease Control and Prevention confirmed that a patient in Louisiana was hospitalized with a severe case of H5N1, as well as another case in Wisconsin.{{Cite news |first1=Jamie |last1=Gumbrecht |first2=Brenda |last2=Goodman |date=18 December 2024 |title=America's first severe case of bird flu confirmed in Louisiana |url=https://www.cnn.com/2024/12/18/health/severe-bird-flu-louisiana-first-us-case/index.html |access-date=18 December 2024 |publisher=CNN |language=en }}{{Cite web |date=18 December 2024 |title=DHS Reports Presumptive Positive Human Case of Highly Pathogenic Avian Influenza (HPAI) in Wisconsin |publisher=Wisconsin Department of Health Services |url=https://www.dhs.wisconsin.gov/news/releases/121824.htm |access-date=18 December 2024 |language=en |archive-date=18 December 2024 |archive-url=https://web.archive.org/web/20241218210807/https://www.dhs.wisconsin.gov/news/releases/121824.htm |url-status=live }} The Louisiana patient later died, becoming the first human fatality to H5N1 to occur in the USA.{{cite news |last1=Dunbar |first1=Marina |title=Louisiana reports first human death in US from bird flu |url=https://www.theguardian.com/world/2025/jan/06/first-human-death-bird-flu-louisiana |access-date=26 February 2025 |agency=The Guardian |date=7 January 2025 }} California governor Gavin Newsom announced a state of emergency due to the rising cases of the bird flu.{{Cite news |date=18 December 2024 |title=Gov. Gavin Newsom declares state of emergency amid bird flu outbreak |url=https://ktla.com/news/california/gov-gavin-newsom-declares-state-of-emergency-amid-bird-flu-outbreak/ |access-date=18 December 2024 |publisher=KTLA |language=en-US |archive-date=19 December 2024 |archive-url=https://web.archive.org/web/20241219081959/https://ktla.com/news/california/gov-gavin-newsom-declares-state-of-emergency-amid-bird-flu-outbreak/ |url-status=live }} The following day, a report of a human case with the bird flu was confirmed in Texas.{{Cite news |last=Malenfant |first=Marley |date=19 December 2024 |title=At least 1 human case of bird flu reported in Texas in latest US outbreak, CDC says |url=https://www.statesman.com/story/news/state/2024/12/19/bird-flu-texas-2024-cases-deadly-severe-symptoms/77083509007/ }}

{{Update section|date=May 2025}}

In January, a 28-year-old man from Kampong Cham province died from H5N1 avian flu infection after possibly consuming symptomatic chickens.{{cite news |last1=Soucheray |first1=Stephanie |title=Cambodian man dies from H5N1 avian flu, possibly after eating sick chickens |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/cambodian-man-dies-h5n1-avian-flu-possibly-after-eating-sick-chickens |access-date=15 February 2025 |agency=CIDRAP |publisher=University of Minnesota |date=11 January 2025 }} In February, a second death from H5N1 occurred in a toddler who had played and slept near sick chickens.{{cite news |last1=Schnirring |first1=Lisa |title=Cambodia reports fatal H5N1 infection in a toddler |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/cambodia-reports-fatal-h5n1-infection-toddler |access-date=26 February 2025 |agency=CIDRAP |publisher=University of Minnesota |date=26 February 2025 }} In March, a 3-year-old boy died from H5N1 after being exposed to and consuming infected chickens.{{cite news |last1=Schnirring |first1=Lisa |title=Cambodia reports third fatal human H5N1 case of the year |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/cambodia-reports-third-fatal-human-h5n1-case-year |access-date=24 March 2025 |agency=CIDRAP |publisher=University of Minnesota |date=24 March 2025}}

India reported a fatal human case of H5N1 in April.{{cite news |last1=Schnirring |first1=Lisa |title=Fatal H5N1 case reported in India's Andhra Pradesh state |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/fatal-h5n1-case-reported-indias-andhra-pradesh-state#:~:text=India%20reported%20its%20last%20human,had%20recently%20traveled%20to%20India. |access-date=4 April 2025 |agency=CIDRAP |publisher=University of Minnesota |date=3 April 2025}}

Mexico reported its first human case of H5N1 infection in April.{{cite news |title=Mexico confirms country's first human case of bird flu in a 3-year-old girl |url=https://abcnews.go.com/Health/wireStory/mexico-confirms-countrys-human-case-bird-flu-3-120505113 |access-date=4 April 2025 |agency=abc |date=5 April 2025}} The patient, a 3 year old girl, died soon after.{{cite news |last1=Li |first1=Yiying |title=Mexico reports first human death from H5N1 bird flu |url=https://www.abc.net.au/news/2025-04-09/first-human-death-from-bird-flu-in-mexico/105154358 |access-date=9 April 2025 |agency=ABC News |date=9 April 2025}}

The UK reported a human case of H5N1 avian influenza in late January which was detected in a poultry farm worker.{{cite news |last1=Schnirring |first1=Lisa |title=UK reports H5N1 in a poultry worker |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/uk-reports-h5n1-poultry-worker |access-date=15 February 2025 |agency=CIDRAP |publisher=University of Minnesota |date=28 January 2025 |archive-date=30 January 2025 |archive-url=https://web.archive.org/web/20250130091857/https://www.cidrap.umn.edu/avian-influenza-bird-flu/uk-reports-h5n1-poultry-worker |url-status=live }} An infected sheep located on an outbreak affected poultry farm was reported in March. Similar to H5N1 in cows, the sheep displayed mastitis and produced milk containing the virus.{{cite news |last1=Schnirring |first1=Lisa |title=UK reports H5N1 in a sheep on poultry-outbreak farm |url=https://www.cidrap.umn.edu/avian-influenza-bird-flu/uk-reports-h5n1-sheep-poultry-outbreak-farm |access-date=24 March 2025 |agency=CIDRAP |publisher=University of Minnesota |date=24 March 2025}}

File:Egg shortage bird flu brooklyn Feb 2025.jpg, New York in February 2025.]]

On 6 January, the Louisiana Department of Health reported the first confirmed bird flu-related death in a human the United States. The victim, an unidentified Louisiana man, had previously been reported sick with the virus in December after being exposed to a combination of infected backyard chickens and wild birds. The man was reported to be over 65 and had underlying health conditions.{{cite web | url=https://www.reuters.com/world/us/louisiana-reports-first-bird-flu-related-death-us-state-agency-says-2025-01-06/ | title=Louisiana reports first bird flu-related death in US | work=Reuters | date=6 January 2025 | last1=Douglas | first1=Leah | last2=Steenhuysen | first2=Julie | last3=Douglas | first3=Leah }} On 12 February, Ohio confirmed their first case, being an adult male, which was then followed by Wyoming Department of Health reporting the first case of bird flu in their state two days later on 14 February, which was a woman.{{Cite web |author=WSYX Staff |date=12 February 2025 |title=Ohio reports state's first human case of bird flu |url=https://abc6onyourside.com/news/local/ohio-reports-first-human-case-of-bird-flu-highly-pathogenic-avian-influenza-mercer-county |access-date=15 February 2025 |website=WSYX |language=en }}{{Cite web |last=Deti |first=Kim |date=14 February 2025 |title=Wyoming's First Human Bird Flu Case Confirmed |url=https://health.wyo.gov/wyomings-first-human-bird-flu-case-confirmed/ |access-date=15 February 2025 |website=Wyoming Department of Health |language=en-US |archive-date=14 February 2025 |archive-url=https://web.archive.org/web/20250214231013/https://health.wyo.gov/wyomings-first-human-bird-flu-case-confirmed/ |url-status=live }} In the last quarter of 2024, 20 million chickens were put down, causing an egg shortage in the following months.{{cite web |title=When will the US egg crisis end? |url=https://www.newsweek.com/when-will-us-egg-crisis-end-2016005 |website=Newsweek |language=en |date=19 January 2025 |access-date=4 March 2025 |archive-date=7 February 2025 |archive-url=https://web.archive.org/web/20250207160909/https://www.newsweek.com/when-will-us-egg-crisis-end-2016005 |url-status=live }}

{{Main|H5N1 vaccine}}

H5-2.3.4.4b can be prevented by vaccination in chickens. In China, The H5-Re14 (2.3.4.4b) strain used in updated vaccines since 2022 is a reasonably good match for the new virus.{{cite journal |last1=Tian |first1=Jingman |last2=Bai |first2=Xiaoli |last3=Li |first3=Minghui |last4=Zeng |first4=Xianying |last5=Xu |first5=Jia |last6=Li |first6=Peng |last7=Wang |first7=Miao |last8=Song |first8=Xingdong |last9=Zhao |first9=Zhiguo |last10=Tian |first10=Guobin |last11=Liu |first11=Liling |last12=Guan |first12=Yuntao |last13=Li |first13=Yanbing |last14=Chen |first14=Hualan |title=Highly Pathogenic Avian Influenza Virus (H5N1) Clade 2.3.4.4b Introduced by Wild Birds, China, 2021 |journal=Emerging Infectious Diseases |date=July 2023 |volume=29 |issue=7 |pages=1367–75 |doi=10.3201/eid2907.221149 |doi-access=free |pmid=37347504 |pmc=10310395 }}

In May 2024, Penn Medicine announced it had created a human avian flu vaccine on the same platform as its COVID-19 vaccine. The experimental mRNA vaccine utilizing lipid nanoparticles (LNPs) had worked to protect lab animals from severe illness and death for at least one year prior to the announcement. It was tested in mice and ferrets, and all vaccinated animals were found to survive H5N1 infections.{{Cite news |url=https://6abc.com/post/university-pennsylvania-creates-human-mrna-bird-flu-vaccine/14886713/ |title=Penn Medicine creates human bird flu vaccine |date=29 May 2024 |access-date=29 May 2024 |publisher=WPVI-TV |archive-date=29 May 2024 |archive-url=https://web.archive.org/web/20240529172923/https://6abc.com/post/university-pennsylvania-creates-human-mrna-bird-flu-vaccine/14886713/ |url-status=live }}{{Cite web |url=https://www.pennmedicine.org/news/news-releases/2024/may/penn-researchers-develop-experimental-mrna-avian-flu-vaccine |title=Penn Researchers Develop Experimental mRNA Avian Flu Vaccine |date=23 May 2024 |access-date=29 May 2024 |last=Geesler |first=Kelsey |website=Penn Medicine News }}{{Cite journal |title=Development of a nucleoside-modified mRNA vaccine against clade 2.3.4.4b H5 highly pathogenic avian influenza virus |journal=Nature Communications |last1=Furey |first1=Colleen |date=23 May 2024 |volume=15 |article-number=4350 |last2=Scher |first2=Gabrielle |doi=10.1038/s41467-024-48555-z |last3=Ye |first3=Naiqing |last4=Kercher |first4=Lisa |last5=DeBeauchamp |first5=Jennifer |last6=Crumpton |first6=Jeri Carol |last7=Jeevan |first7=Trushar |last8=Patton |first8=Christopher |last9=Franks |first9=John |last10=Rubrum |first10=Adam |last11=Alameh |first11=Mohammed-Gabriel |last12=Fan |first12=Steven H.Y. |last13=Phan |first13=Anthony T. |last14=Hunter |first14=Christopher A. |last15=Webby |first15=Richard J. |last16=Hensley |first16=Scott E. |last17=Weissman |first17=Drew |issue=1 |page=4350 |pmid=38782954 |pmc=11116520 |bibcode=2024NatCo..15.4350F }}

• Global spread of H5N1
• List of mammals that can get H5N1
• Avian influenza
• {{annotated link|Yarding}}

{{reflist}}

• [https://www.bbc.com/future/article/20240425-how-dangerous-is-bird-flu-spread-to-wildlife-and-humans 'Unprecedented': How bird flu became an animal pandemic], at BBC Online

{{Influenza|state=collapsed}}

{{DEFAULTSORT:2020-2023 H5N1 outbreak}}

Category:Avian Influenza outbreaks

Category:2020s disease outbreaks