A swan found dead in Scotland has tested positive for the deadly H5N1 strain of bird flu.
AREA ON ALERT
Poultry owners within wild bird risk area must keep birds indoors or, if not possible, ensure they are kept away from wild birds
Bird transport within 6 mile (10km) surveillance zone will be curbed and gatherings banned
Poultry within 1.8 mile (3km) protection zone must be kept indoors and will be tested
The Scottish Executive has extended surveillance zones in Scotland to include 175 properties with 3.1 million birds, as well as free-range poultry.
The dead swan was found in Cellardyke, Fife, eight days ago. Fourteen other birds are being tested.
The H5N1 virus does not currently pose a large-scale threat to humans as it cannot pass easily between people.
But experts fear the virus could mutate to gain this ability, and in its new form trigger a flu pandemic, potentially putting millions of human lives at risk.
Scotland's Chief Veterinary Officer Charles Milne, announcing confirmation of H5N1, said a surveillance zone was being extended to 965 sq miles (2,500 sq km).
The zone contains 175 registered premises, with in total 3.1 million poultry.
About 48 are free-range premises with 260,000 birds.
A total of 14 birds are being checked for bird flu from Scotland including 12 swans and two other species.
Mr Milne said: "There is no indication that any of these are positive."
BIRD FLU FACTFILE
Bird flu viruses have 16 H subtypes and nine N subtypes.
Four types of the virus are known to infect humans - H5N1, H7N3, H7N7 and H9N2
Most lead to minor symptoms, apart from H5N1
H5N1 has caused more than 100 deaths in Cambodia, China, Indonesia, Thailand, Turkey and Vietnam
The World Health Organisation says not all H5 or H7 strains are severe, but their ability to mutate means their presence is "always a cause for concern"
Farmers are being ordered to house their birds where possible, or separate them from wild birds.
However, the Scottish Executive said it would be "disproportionate" to house poultry UK-wide.
Officials were also banning the gathering of birds and enhancing their surveillance.
An initial 1.8 mile (3km) protection zone was set up around Cellardyke on Wednesday, surrounded by a six-mile (10km) surveillance zone.
The infected bird, a native UK breed, was collected from Cellardyke harbour on 30 March - a day after it was reported by a resident.
Mute swans are considered to have a "stable" population in Scotland at this time of year, but Mr Milne said he "cannot entirely rule out" that the swan had migrated.
The Department for Environment, Food and Rural Affairs responded to criticism over the delay in dealing with the dead swan by saying there was no reason to suggest it should be given priority over other samples.
Preliminary work was carried out on Friday in preparation for testing on Monday.
"Where we have specific reason to believe that a sample is infected the labs at Weybridge are open on a 24/7 basis," Defra said.
"It is vital that test results are accurate and, because of the badly decomposed state of this sample, a number of tests were carried out."
Defra said that since 21 February the laboratory at Weybridge had tested more than 1,100 samples.
The UK's chief veterinary officer, Debbie Reynolds, said bird flu could stay in Britain for some time.
"We simply don't know, but of course that's why we've got our programme of wild bird surveillance.
"It's been very extensive; over 3,000 wild birds tested already this year, and over 400 swans.
"There are more under way, being tested at the moment, and any wild swan that's reported found dead should be collected and tested," Dr Reynolds said.
The National Farmers' Union said the presence of H5N1 was an "unwelcome and important development from the point of view of poultry health" but that it was "well prepared".
Liberal Democrat leader Sir Menzies Campbell, whose Fife constituency includes Cellardyke, said the government appeared to have the situation in hand.
Restrictions on the movement of poultry, eggs and other poultry products have been implemented.
It is the first time the strain has been found in a wild bird, but H5N1 was detected in birds held in quarantine in the UK after infected Taiwanese finches arrived at a secure animal unit in Essex in October.
Officials emphasised that the risk to humans was very low.
Scotland's chief medical officer Harry Burns said that eggs and poultry should be "properly cooked" as per usual.
"It's proven very, very difficult for the virus to get into human populations. We know that it doesn't have the right composition to easily infect humans.
"So the arrival of one bird in Scotland does not really add to the risk of this virus emerging as a human strain.
"I will be eating chicken tonight but it will be well-cooked chicken. The evidence from the Food Standards Agency is that in properly cooked meat the virus is killed."
Defra helpline on 08459 335577.