The virus was found in one swan in the Puglia region and one in the Calabria region, both in southern Italy, and in three swans in Sicily, said Health Minister Francesco Storace. The swans had arrived from the Balkans, he said, likely pushed south by cold weather.

"It's certain that the virus has reached Italy," Storace told reporters after briefing the Cabinet on the situation.

Storace said there were no human cases reported and sought to reassure Italians that the outbreak posed no immediate threat to humans as the virus had only affected wild birds.

Poultry Kept Indoors Less Vulnerable

"It's a relatively safe situation for human health, less so for animal health," said Storace.

He did not give the exact number of the birds that had been infected by the virus. But he said most of the 17 swans who were found dead were likely infected with H5N1.

Juan Lubroth, a senior animal health officer at the Rome-based UN Food and Agriculture Organization, said that "for humans, the risk of transmission would be through domestic poultry as contact is more frequent."

"If poultry production practices are such that the animals are kept in open areas in contact with infected wild life, chances of transmission would be higher," Lubroth told The Associated Press. "If poultry is kept indoors, that contact should not occur."

Virus Could Mutate

Testing was conducted at a laboratory in the northern city of Padua, and more analyses were underway, Storace said. Further results were expected as early as Saturday afternoon.

The ministry was looking at taking precautions in the areas where the virus was detected, such as limiting movement of live animals for up to 21 days, Storace said. Random blood tests on poultry in farms would be also carried out in the affected areas.

Bird flu has killed at least 88 people in Asia and Turkey since 2003, according to the WHO. It has been ravaging poultry stocks across Asia since 2003, killing or forcing the slaughter of more than 140 million birds.

Almost all the deaths have been linked to contact with infected poultry, but experts fear the virus could mutate into a form that spreads easily among humans, possibly sparking a pandemic that could kill millions.