Animal disease - major outbreak of highly pathogenic avian influenza

Impact 5
risk indicator
ID 56b
Risk theme Human, animal and plant health
Impact & Likelihood
Impact key
5 Catastrophic
4 Significant
3 Moderate
2 Limited
1 Minor
Likelihood key
5 >25%
4 5-25%
3 1-5%
2 0.2-1%
1 <0.2%


Highly pathogenic avian influenza (HPAI) is a severe, highly infectious influenza causing significant morbidity and mortality in susceptible avian species. Avian influenza is primarily a disease of birds, but can be transmissible to humans through prolonged, direct contact with infected birds or contaminated material. All strains of HPAI are legally notifiable if suspected in the UK, with the biggest outbreak to date being recorded over 2021 to 2023. HPAI is a notifiable disease throughout the UK and anyone who suspects disease in poultry or captive birds must immediately report it. The Animal Plant and Health Agency (APHA) monitors HPAI outbreaks internationally and publishes outbreak assessments considering the risk posed to the UK livestock on GOV.UK.


The reasonable worst-case scenario is based on an outbreak of a highly virulent strain of HPAI that is unlikely to transmit easily to humans. Disease would be introduced into multiple large-scale poultry businesses, through direct or indirect contact with wild birds. Viral spread from both wild birds and between infected premises occurs, leading to an outbreak of 250 large commercial premises in a 6- to 8-month period. About 8 million poultry and captive birds would either be killed by the virus or culled for disease control, and there would be restrictions on trade and exports. Multiple mass-die-off events in wild-bird populations are likely.

Key assumptions

For a strain of HPAI readily transmissible to humans, the public health impact would be handled by the Department for Health and Social Care (DHSC). However, occasional spill-over to humans cannot be ruled out and therefore the local health protection teams would be involved in following up human contacts with each new infected establishment.


A strain of HPAI with greater transmissibility to humans could increase the impact of the outbreak affecting poultry workers, slaughterhouse workers, APHA and contract staff dealing with the outbreaks, as well as those with close contact to wild birds. Disease control measures would need to be adapted to manage the public health risks, with further measures to protect food safety and essential services. The public health impact would be handled by DHSC.

Response capability requirements

Specialist staff including vets, poultry catchers and staff to complete culling, disposal and cleansing and disinfection would be required, along with sufficient transport capacity and access to rendering or incineration. In addition, sufficient laboratory capacity is needed for diagnostic and monitoring purposes; local authority staff to conduct enforcement activities; and modelling experts, epidemiologists, disease experts, wildlife experts, administrators and trained policy staff to support would be
needed. Sufficient personal protective equipment (PPE), respiratory protective equipment (RPE) and approved disinfectant would also be necessary across government and operational partners.


The minimum period to regain regional disease-free status for international trade is a minimum of 28 days from completion of secondary culling and disposal at the last infected premises. Exports to the EU can resume following the completion of enhanced surveillance in the restricted region, usually no less than 30 days after effective culling and disposal of all infected premises in the region. Third- country exports will depend on the relevant bilateral trade agreements. Given the size and duration of this scenario, there would be long-term impacts on trade, the environment, poultry sector, and rural economy