Nov 12, 2007 (CIDRAP News) – Veterinary officials in England today announced an avian influenza outbreak in turkeys at a farm in Norfolk, after initial tests showed that the birds were positive for an H5 strain of the virus.

Officials are awaiting full test results to determine if the turkeys have the highly pathogenic H5N1 strain of the virus, according to a press release from England"e;s Department for Environment, Food and Rural Affairs (DEFRA). Fred Landeg, acting chief veterinary officer, told BBC News today that he expects test results in the next 24 hours.

To date, the deadly H5N1 strain has been identified in British poultry just once, at a turkey farm in February of this year.

The site of the new outbreak is a farm 107 miles northeast of London, near the town of Diss, that also has ducks and geese, DEFRA said. All of the birds will be slaughtered. The number of birds slated for culling is about 5,000, according to the BBC report.

Authorities have established a 3-km protection zone around the farm, along with a 10-km surveillance zone. "We are also urgently considering with ornithological and other experts what wider measures may be needed," DEFRA said.

Landeg said the disease was discovered yesterday when a veterinarian noted an increasing number of turkey deaths in one of the farm"e;s five barns, according to the BBC report. He said the affected birds had access to the outdoors and may have been at increased risk of contracting the disease from wild birds, which migrate in autumn.

A few weeks ago, the chief veterinarian for the United Nations Food and Agriculture Organization warned that apparently healthy geese and ducks in Europe could be harboring the H5N1 virus. He advised authorities in regions that have significant duck and geese production to reinforce their monitoring and surveillance systems.

In the UK"e;s February outbreak, the lethal H5N1 virus was found at the Bernard Matthews turkey operation in Suffolk, about 70 miles northeast of London. The source of the virus, which led to the culling of 152,000 birds, was never conclusively identified, but authorities said it was probably contaminated turkey meat imported from Hungary.

The UK had an outbreak of a different avian flu type in March. In that case, a low-pathogenic H7N2 virus was detected at two small farms, one in northern Wales and one in northwest England. The outbreaks were linked to a handful of mild cases in humans.

The lethal H5N1 virus has turned up in wild birds in Britain once, in a swan found dead on the coast of Scotland in March 2006. Also, the virus was identified in October 2005 in a parrot that had been imported from Suriname and quarantined in Essex with birds imported from Taiwan.