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
• 993 human cases and 477 deaths across 25 countries since 2003 (WHO)
• 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: 30+ mammal species worldwide, and 94 bird species in the Americas alone between Jan 2025 and Mar 2026

Australia was the last inhabited continent free of H5N1 until 20 June 2026, when it was confirmed in wild migratory seabirds at Cape Le Grand National Park in Western Australia. On 29 July 2026 the outbreak passed its defining threshold: the Consultative Committee on Emergency Animal Diseases agreed, on CSIRO testing and sequencing, that local transmission has occurred between greater crested terns resident in South Australia, the first local transmission of H5 anywhere in Australia. The next morning Victoria became the fifth state to detect the virus, in a greater crested tern near Portland, and CSIRO confirmed South Australia's 15th case in a giant petrel at Port Lincoln on the Eyre Peninsula. South Australia has a further 24 suspected cases with CSIRO, including six greater crested terns at Seal Bay on Kangaroo Island, beside an endangered Australian sea lion colony where on-beach tours remain paused. Australia's Chief Veterinary Officer has said that in the natural environment there are limited feasible actions to contain the spread and that losses in susceptible wildlife cannot be avoided, leaving surveillance as the primary response. There are still no detections in poultry or the wider agricultural sector, no mass mortalities, and human health risk remains low.

• Key Facts
• First detection 20 Jun 2026 at Cape Le Grand NP, WA (clade 2.3.4.4b)
• Local transmission between resident Australian birds was confirmed on 29 Jul 2026, the first time the virus has been shown to spread within Australia
• 28 confirmed or presumed-positive wild-bird detections: 10 WA, 15 SA, 2 NSW, 1 QLD (as at 30 Jul)
• Victoria detected its first case on 30 Jul 2026, a greater crested tern near Portland, and has enacted its State Emergency Animal Disease Response Plan. CSIRO confirmation is pending, so it is not yet in the national tally
• SA's 15th confirmed case, a giant petrel at Port Lincoln, is the first on the Eyre Peninsula and a long westward jump from the Limestone Coast and Kangaroo Island clusters
• 24 suspected cases in SA are with CSIRO, all greater crested terns, including six at Seal Bay on Kangaroo Island over two days
• On-beach tours at Seal Bay Conservation Park remain paused to protect an endangered Australian sea lion colony of about 1,000 animals, from a species with about 12,000 individuals left
• More than 150 native bird species and more than 10 mammal species have been assessed at very high risk of extinction or major decline if infected
• The Chief Veterinary Officer says containment in the natural environment is not feasible and the focus is on surveillance to confirm where the virus is circulating
• No commercial-poultry detections and no mass mortalities. About $113m committed to preparedness, plus a further $24m released to states and territories on 29 Jul

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 180 million poultry lost since 2022 (about 19 million in the last 30 days)
• About 973 dairy herds across 17 states since the March 2024 cattle jump
• 71 human cases and 2 deaths, predominantly farm workers
• Viral fragments found in about 1 in 5 retail milk samples; pasteurisation inactivates it

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
• 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)