Scientists and veterinary experts were today discussing how to reinforce the European Union's protection against the avian flu virus, which has evaded existing measures to spread into five member states.

Germany and Austria last night became the latest countries to report that preliminary tests on dead swans had revealed presence of the fatal H5N1 strain, which has killed about 80 people in South East Asia and Turkey.

Tests to confirm the German and Austrian results were continuing at the EU’s monitoring laboratory in Weybridge, Surrey.

The strain - which scientists fear could mutate into a virus capable of being passed between humans - has also been found in wild birds in Greece, Italy, and Slovenia in the past few days as migrating swans are driven south by freezing weather in northern Europe.

The German samples were recovered from two dead swans found on the Baltic Sea island of Rügen, off the German coast. Authorities in Austria have also recorded the presence of the highly pathogenic strain in the southern city of Graz.

All five affected countries instantly introduced the EU's defence measures, which involve a halt to poultry movements in the affected region, and the construction of a two-mile protection zone and four-mile surveillance zone around the site of the disease.

In the protection zone, all poultry must be kept indoors and cannot be transported except to slaughterhouses. Hunting wild fowl is banned.

Authorities in Sweden and Denmark have also ordered all poultry and tame birds to be kept indoors as bird flu rapidly approaches their borders.

Experts on the EU’s Standing Committee on the Food Chain and Animal Health were beginning two days of talks to examine what other precautionary and surveillance measures, if any, could be taken. This morning, they agreed to back enhanced aid packages for better surveillance of wild birds and a ban on imports of untreated feathers.

They are also assessing the potential for far more discoveries of the virus during the spring migration season, when wild birds fly north.

Two children have died from H5N1 infection in Turkey this year. The virus has killed at least 91 people in Asia and Turkey since 2003, according to the World Health Organisation. Almost all the human deaths have been linked to contact with infected poultry.

As the virus continued to march west into Europe, scientists in Indonesia reported that it appeared to be becoming more potent: victims are dying more quickly and in greater numbers.

Anton Apriyantono, the Indonesian Agriculture Minister, said: "This means the virus is getting more ferocious," as he announced plans to step up surveillance.

Mr Apriyantono provided no data to back up the assertion, but World Health Organisation figures for this year show eight human cases of bird flu in Indonesia, seven of which were fatal. In 2005, there were 17 cases and 11 deaths.

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