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 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. Seven weeks later the response has changed footing. On 29 July the Consultative Committee on Emergency Animal Diseases agreed that local transmission had occurred between greater crested terns resident in South Australia. On 31 July aerial surveillance found 49 dead and 35 sick terns on Baudin Rocks near Cape Jaffa, and on 3 August CSIRO testing confirmed it as the first mass mortality event of the outbreak. A second suspected mass mortality event is under investigation in Victoria. The virus is now moving off the coastline: a magpie in Victoria on 6 August was the first detection in a terrestrial bird, a tern found near Wentworth in far west New South Wales on 8 August, at the junction of the Murray and Darling rivers, is the furthest-inland detection yet and the first in the Murray-Darling Basin, and a cormorant at Carpenter Rocks on 10 August added a seventh wild bird species, a waterbird equally at home on inland rivers. The national tally has gone from 28 confirmed detections on 30 July to 231 as at 1pm AEST on 10 August, with 163 in South Australia and 53 in Victoria, and the two largest daily rises of the outbreak came on consecutive days, 52 on 7 August and 40 on 8 August. Victoria has ordered poultry owners with 50 or more birds in metropolitan Melbourne and coastal areas to house them, the first mandatory housing order by any Australian jurisdiction, and the Royal Adelaide Show has cancelled its bird and poultry exhibits. Eradication in wildlife is no longer considered feasible, and the Commonwealth, states and territories have activated a cost-shared national management agreement to manage the disease in wildlife for the long term. A federal risk assessment released on 5 August scores about 300 species and subspecies at high to extreme risk. There are still no detections in poultry or livestock anywhere in Australia.

• Key Facts
• First detection 20 Jun 2026 at Cape Le Grand NP, WA (clade 2.3.4.4b). Australia was the last inhabited continent the virus reached.
• 231 confirmed wild-bird detections: 10 WA, 163 SA, 4 NSW, 1 QLD, 53 VIC (DAFF, as at 1pm AEST 10 Aug 2026). The figure moves within a single day, so the as-at time matters as much as the date.
• The three days to 10 Aug added 76 detections, with the two largest daily rises of the outbreak on consecutive days: 52 on 7 Aug and 40 on 8 Aug. Nearly all were sited by the department, most on South Australia's Limestone Coast and Kangaroo Island.
• Two greater crested terns confirmed in NSW on 8 Aug are the state's first cases in native birds. One, found near Wentworth at the junction of the Murray and Darling rivers, is the furthest-inland detection in Australia and the first in the Murray-Darling Basin, opening the continent's inland wetlands to spread ahead of spring breeding.
• The species list keeps widening: a magpie in Victoria on 6 Aug was the first terrestrial bird, and a cormorant at Carpenter Rocks, SA on 10 Aug became the seventh wild bird species, a fish-eating waterbird as at home on inland rivers as on the coast.
• Local transmission between resident Australian birds was confirmed on 29 Jul, and the first mass mortality event followed on 3 Aug at Baudin Rocks, SA, where 84 birds were found dead or dying. It adds only 6 to the national tally because just a sample was collected, so the detection count is not a death count and the real toll runs well above the headline figure.
• Eradication of H5 in Australian wildlife is no longer considered feasible. On 5 Aug the Commonwealth, states and territories activated a cost-shared National Management Agreement, moving from eradication to long-term management.
• No commercial-poultry detections anywhere in Australia. Victoria became the first jurisdiction to order mandatory poultry housing on 7 Aug, covering owners of 50 or more birds in metropolitan Melbourne and coastal areas for an initial 14 days, and the Royal Adelaide Show has cancelled all bird and poultry exhibits.
• A federal risk assessment released 5 Aug scores about 300 species and subspecies at high to extreme risk, among them the little penguin, Australian sea lion and orca. More than 2 million migratory birds arrive from the north from September, and whether H5 establishes in freshwater waterbirds is the variable that decides severity, because overseas it was ducks that turned coastal outbreaks into continental ones.
• No Australian mammal has a confirmed detection. Four are under investigation, most recently a seal pup that died at Warrnambool on 6 Aug. A count of investigations is not a count of cases.

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.