A man diagnosed with a severe form of pneumonia known as legionnaires' disease died in Russia's Urals town Wednesday, bringing the death toll to four since the outbreak was reported July 19, local health officials said.

"One more patient died of legionellosis in the town of Verkhnyaya Pyshma," the Health Ministry in the Sverdlovsk Region said. "The number of victims of the infection has reached four."

A total of 150 people from 18 to 81 years of age have been hospitalized with the suspected disease since mid-July. Four people are in intensive care, the ministry said.

But health officials said the disease was subsiding as people with a suspected light form of the pneumonia have been brought to the hospital in the last few days. "Their hospitalization has been a kind of excessive precaution," officials said.

Hot water supplies, believed to be the origin of the infection, have been suspended in the town to prevent the disease from spreading, Russia's chief sanitary doctor, Gennady Onishchenko said on television Tuesday. An investigation is continuing.

Legionnaires' disease acquired its name in 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion in Philadelphia.

It can be contracted by breathing mist from water that contains the bacteria. The mist can come from hot tubs, showers or air conditioning. The bacteria do not spread from person to person.