France's health minister urged vigilance on Thursday after tests on three dead swans in the northeast confirmed an outbreak of the H5N1 strain of bird flu, which can be fatal to humans.
"France is not threatened by a bird flu pandemic as there has not been, for the moment, a human contamination from the H5N1 virus," Health Minister Roselyne Bachelot said.
But she added "we must be vigilant as the great flu epidemic that followed the war of 1914, the Spanish flu" came from a strain of bird flu.
Scientists believe a strain related to today's bird flu virus killed tens of millions of people during the Spanish flu pandemic.
"We must do what is necessary to ensure that all of the agencies, the entire health system is ready to deal with a mutation of the virus" that could attack humans, said Bachelot on French television.
Tests on the three swans found dead last week in northeast France confirmed the presence of the H5N1 strain of bird flu, the agriculture ministry said in a statement.
Agriculture Minister Michel Barnier said the threat level from bird flu would be raised from "moderate" to "high" following the results of the tests.
"The national laboratory of the French agency for animal health has confirmed the presence of the H5N1 highly pathogenic virus on the three swans found dead in a pond near the town of Assenoncourt," said a ministry statement.
France had stepped up surveillance after several cases of the H5N1 virus were discovered in Germany and the Czech Republic last month.
Authorities had sealed off the pond in the Moselle department where the birds were found last week.
In accordance with EU norms, a one-kilometre (0.6 mile) exclusion zone has been established around the Assenoncourt pond, as well as a wider 15-kilometre "observation" zone.
France's only outbreak of H5N1 was early last year, when it was detected in 62 dead wild birds, contaminating a turkey farm in central France.
The World Health Organization has reported 317 cases of bird flu in humans, of which 191 resulted in death, according to its June 29 tally. Indonesia, Vietnam and Thailand top the list of most affected countries.