A mass influenza outbreak has killed six patients at a hospital in Akita Prefecture where about 80 others, including inpatients and staff, have been treated for infection, the prefectural government said Saturday.

The four — two men ranging in age from 60 to 90 and two women between 70 and 80 — tested positive in simple flu tests before succumbing between Oct. 31 and Friday at Takanosu Hospital in Kitaakita, the prefectural government said on the day.

A local health center confirmed in further tests that one of the patients had contracted the Hong Kong A-type flu.