Migratory ducks and waders could bring bird flu to Britain this winter, experts have warned, after the disease was found in wild flocks in Russia.

The potentially lethal avian flu virus, H5N1, is now spreading westwards after health experts in Siberia and Kazakhstan discovered outbreaks of the virus in birds that will soon enter Europe. Yesterday, as the total number of confirmed cases in Russia hit 40, the authorities revealed the first suspected case of the virus at a commercial chicken farm in the western Siberian region of Omsk. Another 78 villages have suspected cases.

The disclosure is likely to force European governments to step up control measures. The Dutch authorities have already ordered all poultry farmers to bring their chickens indoors from tomorrow, and the German government announced on Friday it would order all its poultry farmers to follow suit next month if the virus spread.

British bird experts have told The Independent on Sunday they believe there is a risk - although currently a small one - that migratory ducks and waders arriving in the UK this autumn will be carrying the disease. Health experts are increasingly alarmed about the dangers of its spread because nearly nine million water-birds and waders migrate from Siberia to Europe every autumn, with nearly 850,000 thought to make winter homes in Britain.

Some species, including the pochard duck, identified as one of the birds that brought the disease from elsewhere in Asia to Russia, breed in the affected areas. British ornithologists and the National Farmers Union (NFU) are now closely tracking the new outbreaks, and have drafted new measures to control an outbreak in bird sanctuaries and chicken farms.

The NFU admits it is also preparing plans to bring poultry indoors if the virus arrives in Britain, which could be quickly stepped up to include mass culls on infected farms. Bans on imports of all Russian poultry into the EU have already been imposed.

The risks of the virus being spread by wild birds will be high on the agenda of the Government's expert animal diseases advisory committee meeting this November. The Department of the Environment, Food and Rural Affairs is also planning a major national emergency exercise early next summer, to plan for a nationwide outbreak.

Andy Evans, of the Royal Society for the Protection of Birds, said conservationists were updating their plans as they tracked the outbreak in Russia. "It's evolving as rapidly as events unfold," he said.

Dr Ruth Cromie, a biologist with the Wildfowl and Wetlands Trust, said the spread of the virus to Europe could be slower than many fear because many birds with the disease would die en route. Most birds migrating from currently affected areas would fly southwards to the Mediterranean and north Africa, so the chances of it arriving in Britain this winter was "very slim indeed".

The fear was that the virus would spread within Russia to the northern Siberian regions where birds which flew to Britain nested. "There is a possibility of it spreading. It's important for us to be prudent with bio-security," she said.

Although the chances of the virus spreading from birds to humans within Britain is thought to be very low, the Cabinet's civil disasters committee, Cobra, is to stage its own emergency exercise next month.

Ministers and the World Health Organisation believe a global flu pandemic in the next few years is inevitable and fear it could potentially cause millions of deaths worldwide and hundreds of thousands in Britain.

Additional reporting by Gemma Collins