One person caught the bird flu virus while working at a contaminated poultry farm after an outbreak in Japan last February, in the first case of human infection confirmed in Japan, the government said Wednesday.

The Health Ministry said blood samples taken from five Japanese earlier this year were tested for avian influenza, and one had antibodies for the disease, confirming the infection. The four others were probably infected but tests weren't conclusive.

It was the first confirmed case of human infection from the disease in Japan, the ministry said in a statement, which did not reveal when the confirmation was made.