Tape instructing members of the public to keep out marks the entrance to a farm where an outbreak of H7N7 avian flu was detected in the village of Goosnargh, near Preston, north west England on July 13, 2015. (OLI SCARFF / AFP)

LONDON - Britain declared a nationwide Avian Influenza Prevention Zone on Wednesday, ordering farms and bird keepers to toughen their biosecurity measures after a number of cases of bird flu were spotted in wild birds.

ALSO READ: France sees bird flu outbreak as virus spreads again in Europe

The government said it was now a legal requirement for all bird keepers in Britain to follow strict measures, with keepers of more than 500 birds needing to restrict access for non-essential people. Areas must also be cleaned regularly.

READ MORE: Ghana detects bird-flu outbreak with 600,000 animals at risk

The government said the risk to public health from the virus was very low.