Milwaukee Health Department looking into Legionnaires' breakout UPI 7/18/2013 4:42:11 PM MILWAUKEE, July 18 (UPI) -- The Milwaukee Health Department is looking into an outbreak of Legionnaires' disease that has affected 20 people, officials said. So far, 20 adults in Milwaukee County have been confirmed to have the disease, which is a severe form of pneumonia caused by a bacterium known as legionella, since June 1, the Milwaukee Journal Sentinel reported Wednesday. Most of those people were infected in early June, but about six people were infected in early July, said Paul Biedrzycki, director of disease control and environmental health for the Milwaukee Health Department. No deaths have been reported due to the outbreak. Milwaukee Health Department is looking for the environmental source, as Legionnaires' disease is not spread person to person, but by inhaling the bacteria. The legionella bacteria naturally occurs in stagnant water, especially in hot, humid weather, Biedrzycki said. "It also could be from a water source not routinely disinfected or treated... We're moving toward what is the common thread or source," Biedrzycki said. Milwaukee Health Commissioner Bevan Baker said that while there is not a widespread threat, the threat of more people becoming infected is ongoing. "This is a naturally occurring bacteria and we see a handful of these cases every year," Baker said. "This is not atypical." Symptoms of Legionnaires' disease include chest pains, shortness of breath, nausea including vomiting and diarrhea and usually begin two to 14 days after a person is exposed to the bacteria.