Defra has today published its preliminary epidemiology report into the case of H5N1 avian influenza in mute swans at the Abbotsbury Swannery, Dorset. Though the source of infection has not been identified, one hypothesis is that wild birds moving from the continent may have carried the virus to the UK.

The H5N1 virus is believed to have evolved in poultry and, worldwide, it has been transmitted in a number of ways, including movements of poultry and poultry products, the trade in captured wild birds (now banned in the European Union), direct human transfer and contact between wild birds and poultry.

Although there are both mute swans and other waterfowl present at the Swannery, the virus has only been found in six swans found dead. Samples from 60 live trapped swans and faeces from other waterfowl have tested negative. There has been no virus detected to other wild birds or domestic poultry in the vicinity.

There is much more we need to know about avian influenza in the UK, and the birds at Abbotsbury Swannery present a unique opportunity to increase our understanding of the transmission and impacts of this virus. Testing live swans for the disease was a good first step. We will support efforts by Defra to monitor progress of the virus amongst the swans at the Swannery over the coming weeks.

Surveillance for avian influenza continues on RSPB nature reserves across the UK, in order to ensure that the poultry industry and other interests have the earliest possible warning of new outbreaks. We are grateful to Scottish Natural Heritage for recognising our efforts and making a significant contribution towards our monitoring costs in Scotland.