Up to 77 people in Japan may have been infected with a mild form of bird flu, Kyodo News agency reported Tuesday, citing government officials.
The sufferers came from two prefectures - Saitama and Ibaraki - outside of Tokyo, the report said. Officials at the Health Ministry refused to immediately confirm the report.
Kyodo said the 77 showed evidence of antibodies to the H5N2 virus, which is weaker than the deadly H5N1 form.
That virus has killed at least 76 people worldwide since 2003, according to the World Health Organization's Web page.
Japan so far has suffered one case of human infection of the more deadly virus, but no deaths.