H5N1 Avian Influenza

H5N1 (clade 2.3.4.4b) is the most widespread bird-flu panzootic on record. Since 2021 it has moved through wild birds and poultry on every continent, crossed into dozens of mammal species and, in 2024, established a sustained reservoir in US dairy cattle. Human cases stay rare and mostly occupational, but the reach of the virus and its repeated jumps into mammals keep global pandemic-preparedness attention high.

• Key Facts
• 1,000 human cases and 479 deaths across 25 countries since 2003, a 47.9 percent case fatality ratio (WHO cumulative table, data in HQ as at 7 Jul 2026).
• More than 2,000 animal outbreaks reported by 64 countries and territories in 2025 to 2026 (WOAH State of the World's Animal Health 2026)
• Ongoing panzootic of clade 2.3.4.4b, now on every continent including Antarctica
• First H5N1 in dairy cattle recorded in the US in March 2024
• Reached Australia in June 2026 and New Zealand in July 2026, the last continents affected
• Australia confirmed local transmission between its native birds on 29 Jul 2026, the step that has preceded establishment on every other continent
• About 140m farmed birds have died or been culled worldwide since January 2025
• Detections span both birds and mammals: more than 60 mammal species worldwide, and 94 bird species in the Americas alone between Jan 2025 and Mar 2026.

Australia is eleven weeks into its first H5N1 incursion, the last inhabited continent the virus reached. Spread among resident native birds in all six states has entered a mass-mortality phase: more than 1,000 terns were found dead on three South Australian islands this week, and 28 penguins found dead on Tasmania's King Island await test results. Eradication has been abandoned in favour of long-term management, and vaccination of priority species is under way. There are 277 confirmed detections as at 20 August 2026, with the true toll now running thousands higher. No poultry, livestock or human cases.

• Key Facts
• First detection 20 Jun 2026 at Cape Le Grand NP, WA. Australia was the last inhabited continent the virus reached.
• 277 confirmed detections across six states as at 20 Aug 2026: SA 177, VIC 74, TAS 11, WA 10, NSW 4, QLD 1, derived from state figures.
• Mass mortalities have arrived at scale: more than 1,000 terns died on three remote SA islands, and 28 King Island penguins await results. Only sampled birds enter the count, so the true toll runs thousands above it.
• Nine wild bird species are affected, including a magpie, a cormorant, a fluttering shearwater and the first Phillip Island little penguin, found dead on 15 Aug.
• The virus is inland as well as coastal, with detections at Wentworth, Mildura and Hamilton putting it in the Murray-Darling Basin.
• Tasmania, the sixth state, holds 11 cases, most on King Island in Bass Strait, where a suspected penguin mass mortality is being tested.
• Eradication in wildlife is judged not feasible; a cost-shared national management agreement now governs the response.
• Vaccination of captive native species has begun, and up to 5,000 Phillip Island and St Kilda penguins started receiving doses on 17 Aug.
• Victoria ordered the first mandatory poultry housing. There are no poultry, livestock or human cases anywhere in Australia.
• Federal reporting moved to an event basis on 12 Aug and counts 251 positive events as at 17 Aug; detection counts now come only from state agencies.

The United States hosts the largest and most entrenched animal H5N1 outbreak in the world, the reference case for an uncontrolled incursion. Established in wild birds since 2022, it has driven the loss of more than 180 million poultry and, in March 2024, made an unprecedented jump into dairy cattle, now about 973 herds across 17 states. That mammalian reservoir has produced 71 human cases and 2 deaths, almost all in farm workers.

• Key Facts
• More than 200 million poultry lost since 2022, the world's most severe animal H5N1 outbreak.
• 1,166+ dairy herds across 19 states since the March 2024 cattle jump, the world's first H5N1 in cattle. Idaho now leads; California has had no new infected herd since Nov 2025.
• 71 human cases and 2 deaths per CDC, mostly dairy and poultry workers. WHO's cumulative table records the same 71 cases but 1 death.
• Viral fragments found in about 1 in 5 retail milk samples; pasteurisation inactivates it.
• More than US$1.19bn paid in federal reimbursements to farmers.
• Figures are as at 22 Jul 2026. APHIS and CDC block automated access, so this region is refreshed by hand and may lag the others.

The United Kingdom has sustained, seasonal H5N1 activity in wild birds and poultry. Around 100 confirmed cases were recorded across the 2025/26 season, most of them in England. Mandatory housing orders were lifted on 9 April 2026 and the avian influenza prevention zone on 4 June 2026, though fresh commercial outbreaks followed in eastern England. The UK also reported the world’s first H5N1 infection in a sheep.

• Key Facts
• About 100 confirmed H5N1 cases across the 2025/26 season, 79 of them in England
• Mandatory housing orders lifted 9 Apr 2026 and the prevention zone lifted 4 Jun 2026
• Fresh commercial outbreaks followed in eastern England (Lincolnshire, Gainsborough)
• World’s first H5N1 infection in a sheep, on a poultry-outbreak farm

Across the EU, H5N1 activity in the 2025/26 season is easing into summer after widespread circulation in wild birds and poultry. Poland has recorded the most outbreaks, followed by France and the Netherlands. The EU has moved further than most regions on human preparedness, securing around 40 million vaccine doses across member states, and in 2024 Finland became the first country in the world to offer H5 vaccination to exposed workers.

• Key Facts
• 2025/26 season easing into summer after widespread circulation
• 949 A(H5) detections across 30 countries between 28 Feb and 4 Jun 2026, 763 in wild birds and 186 in domestic (EFSA/ECDC quarterly, published 26 Jun 2026).
• Poland leads with 143 outbreaks, then France (20) and the Netherlands (18)
• EU has secured around 40 million vaccine doses across member states
• Finland ran the world’s first human H5 vaccination programme in 2024

New Zealand recorded its first ever H5N1 case on 15 July 2026, a brown skua near Wellington, roughly four weeks after Australia. A native swamp harrier followed within days. With many endemic birds flightless, ground-nesting and already endangered, MPI warns the virus is likely to become endemic within months and has begun vaccinating core populations of its most at-risk species.

• Key Facts
• First case 15 Jul 2026, a brown skua at Petone Beach, Wellington
• First native bird 17 Jul, a kāhu (swamp harrier) in the Wairarapa
• Mainland Poultry locked down more than 550,000 free-range hens
• About 300 core birds of 5 endangered species being vaccinated (takahē, kākāpō)
• No further detections since 17 Jul 2026, and none in poultry.