An outbreak of Legionnaires' disease at a spa in Hyuga, Miyazaki Prefecture, claimed its first fatality when a man in his 70s died early Thursday, prefectural officials said.

The disease struck visitors to Hyuga Sun-Park Onsen, which opened to the public July 1 but was shut down July 24 after reports linked it to the disease outbreak.

Some 20,000 people are estimated to have used the facility during the period.

The prefecture said 16 people have the infection, including four whose condition was confirmed Wednesday. One of them is from neighboring Kagoshima Prefecture and three from Miyazaki.