Almost 1.8 million farmed and captive birds have been culled in the past three months because of the spread of avian flu across the UK, the BBC has learned. There have been 33 outbreaks of the virus on farms and, on Wednesday, the government said bird-keepers in five more English counties would have to house flocks indoors from Sunday.

A new CDC report found evidence of previous bird flu infection in veterinary practitioners who work with cattle and who did not know they had been exposed.