Japan’s Health Ministry said on Wednesday that at least one person had been infected with the bird flu virus after an outbreak among chickens in February but that there was no chance that this person would infect others.

The ministry said four others had also probably been infected with the virus, but added that none of the five had developed any symptoms of bird influenza.

The case marks the first human infection of the bird flu virus in Japan. The H5N1 strain of bird flu has killed 32 people in Vietnam and Thailand this year.

“We think that one person has been infected,” a Health Ministry official told a news conference, adding that chances are high that four others were also infected in a February outbreak at a poultry farm in Kyoto in western Japan.

The assessment was based on a survey of 58 people who took part in tasks such as disposing of dead chickens after the outbreak. The survey included blood tests conducted in April.

The Health Ministry said on Saturday that five people - four workers at the poultry farm in Kyoto and a local government employee - had tested positive for an antibody to the virus.

The five patients probably did not take proper preventive steps such as wearing special masks and taking anti-flu drugs when they came into contact with dead birds or contaminated areas, officials said.

“Proper protection is necessary and I think that’s the point from this case that we can apply in the future,” said Nobuhiko Okabe, a director for the National Institute for Infectious Diseases who attended the same news conference.

NO CONTAGION

There was no sign that any of the five had caught the virus from another person, officials said. The Health Ministry added there was no risk of them infecting others.

“The five people who tested positive for antibodies have not developed symptoms of bird influenza and there is no risk of them developing symptoms in the future. And there is no possibility they will infect others,” the ministry said in a statement.

“We don’t think it is a problem for public health.”

Koichi Otsuki, a professor of veterinary microbiology at Tottori University in western Japan, agreed.

“We have not heard that there was any transmission from one person to another. With regard to the case in Kyoto, I don’t think there was any risk of a mutation into a new virus as the WHO has been worried about,” Otsuki, who was not involved in the Health Ministry study, told Reuters.

The World Health Organization and health officials around the globe fear that the H5N1 strain might mutate into a lethal new virus that could spread rapidly among humans.