Japan’s Health Ministry reported that 93 poultry farm workers may have been exposed to a mild form of the bird flu virus last year.
The ministry had said in a preliminary report in January that 77 people were exposed to and possibly infected with the H5N2 strain, which was not previously known to infect humans. It is milder than the virulent H5N1 strain that has recently spread from Asia to Europe.
Most of the 77 were poultry farm workers in Ibaraki and Saitama prefectures (states) near Tokyo.
After conducting tests on more workers, the ministry found that 16 more in Ibaraki may have also caught H5N2, according to ministry official Hiroshi Takimoto.
Preliminary tests on the workers were positive for H5N2 antibodies, indicating they were previously exposed, Takimoto said.
While exposure carries with it the possibility of infection and illness, he said none had tested positive for the virus itself or had developed flu symptoms.
The ministry had been testing chicken farm workers since a bird flu outbreak in Ibaraki in June last year.
About 5.7 million birds have been destroyed in Ibaraki following the H5N2 outbreaks.