Several farms were sealed off in eastern France and tighter rules were applied to poultry breeders yesterday after three dead swans tested positive for the virulent H5N1 strain of bird flu.

The first instance of bird flu in France since early 2006 followed the discovery of a case in eastern Germany on Tuesday. Wild birds in Bavaria and Saxony also died from the disease last month. Within the European Union bird flu has also been found this year in Hungary, Britain and the Czech Republic.

Police sealed off farms close to the village of Assenoncourt in the Moselle region, where the swans were found by a pond a week ago. Local veterinary experts said that the birds were young, born this spring, and had not arrived with migration.

The Government raised its alert level to high. This means that birds and poultry in mainland France, Europe’s biggest poultry producer, must be locked up or protected by nets to avoid contact with wild birds.

An eight-mile observation zone was set up around Assenoncourt but a spokesman for the local council said that no other dead birds had been found since the swans. Pigeon races and other events where birds are gathered will be forbidden.

Bird flu, which is believed to spread along migration routes, can be fatal to human beings who have been in direct contact with infected animals. France had already stepped up precautions after the recent discovery of infected birds in other European countries.

Roselyne Bachelot, the Health Minister, said that France was not threatened by a flu pandemic but that the Government was on alert. “We have to be extremely vigilant because the large flu epidemic that appeared after World War I, also known as Spanish flu, was of avian origin.”

Last year 13 EU states confirmed bird flu cases – Germany, Austria, Denmark, Italy, Greece, Britain, the Czech Republic, Poland, Slovakia, Slovenia, Sweden, France and Hungary.

In France the virus was found in February last year in more than 60 wild birds and at a farm with 11,000 turkeys. More than 30 countries have reported outbreaks in the past year, in most cases involving wild birds such as swans.

The H5N1 virus has killed more than 190 people worldwide, according to the World Health Organisation. None of the victims was from Europe. The countries that have experienced the most serious outbreaks of bird flu are Indonesia, Vietnam and Thailand.

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