TOKYO - The Japanese Health, Labor and Welfare Ministry reported Wednesday that one of five people suspected of having been infected with bird flu at a chicken farm in Kyoto prefecture was the first person confirmed to have carried the virus in the country.
Although the ministry said it was "highly likely" that the other four had been infected, it added that none of them displayed symptoms and there was no risk of secondary infection.
It was feared that four employees of Asada Nosan, a poultry company, and a Kyoto prefecture government official had been infected with the pathogenic bird flu virus in February, when the disease spread among chickens at the company's Funai Farm in Kyoto prefecture.
The ministry and other health authorities examined 58 people - 16 farm workers who slaughtered chickens and 42 government officials who entered the farm to sterilize it. Blood samples detected antibodies to the virus in five people.
The ministry believes the man was infected with the virus because he worked at the farm without wearing protective clothing before the company reported the disease to the prefecture government.
The ministry sent notices to local governments Wednesday, urging them to take protective measures for concerned people immediately when an outbreak of bird flu was suspected.
At a news conference the same day, Mitsuhiro Ushio, head of the ministry's section in charge of infectious diseases, called for calm.
"There's no risk that a person could develop symptoms of bird flu. It's also unlikely that he would infect others with the disease," he said.
The highly pathogenic strain of bird flu appeared at Funai Farm in late February. The ministry said it was almost certain that the man was infected with the virus during that period.
Medical experts said that if the bird flu virus mutates, it could lead to the appearance of a new type of influenza to which human beings have no immunity, creating serious problems.
Last month, the World Health Organization issued a warning, saying the risk of a new type of flu appearing is the highest in recent years. In light of this, medical experts said that the confirmation of the infection had significance.
They said one of the lessons learned from the nation's first case of human infection with bird flu was the importance of the initial response.
After noticing that a large number of chickens were dying, Funai Farm officials left the situation unattended for a week. Asada Nosan managers later faced criminal charges.
According to the ministry, farm employees worked without protective suits or masks for a while before infection among the chickens was officially confirmed. On the other hand, government officials were fully protected when they visited the farm to dispose of the infected chickens and investigate.
Though one of them was judged to be highly likely to be infected, none has been confirmed to carry the virus.