From 2021-2024, the UK experienced its worst ever outbreak of avian influenza (also known as 'avian flu' or 'bird flu'), affecting at least 78 bird species (RSPB, 2024) with millions of birds dead worldwide. The virus is also known to have infected 26 mammal species such as mink, bears, elephant seals, and cows (Bourke, 2024). This spread to mammals was likely a result of predators eating infected birds (EFSA et al, 2023). 

Avian flu spreads between birds through exposure to infected droppings/saliva, or through bird-on-bird predation (RSPB, 2024). Different species of birds vary in susceptibility to the disease; for example small garden birds are believed to be at quite low risk, while waterfowl, seabirds, and poultry are at high risk (EFSA et al, 2023; RSPB, 2024).

The virus was first noted in 1996 in intensive bird farming facilities, and since then multiple strains of the virus have developed (NHS, 2022; RSPB, 2024). The most recent strain is named 'Highly Pathogenic Avian Influenza (HPAI)', and is responsible for the recent outbreaks in the UK (RSPB, 2024). Some of the latest research shows that UK breeding populations of great skua (Stercorarius skua), Northern gannet (Morus bassanus), sandwich tern (Thalasseus sandvicensis) and common tern (Sterna hirundo) have been significantly impacted by HPAI in particular (Tremlett et al, 2025).

Over the last 20-30 years, thousands of cases of humans being infected by avian flu have been reported, however the virus does not spread easily between people (NHS, 2022; Skufca et al, 2022). Humans may catch the virus by touching infected birds, faeces or nests, or eating infected meat, although the thorough cooking of meat removes the risk of infection (NHS, 2022; RSPB, 2024). Generally, these cases occur where people are living or working in close contact with birds. Overall the risk to humans is low, as there is no evidence of person-to-person transmission, and can be kept to a minimum by avoiding contact with sick birds (Skufca et al, 2022; EFSA, 2023). 

The most recent outbreak of HPAI in Scotland was confirmed in January 2025 near Kirriemuir, Angus (Scottish Government, 2025).  There are still ongoing outbreaks globally, with a new strain recently detected in Texas cattle as of April 2024 (Bourke, 2024).