City health officials are investigating an outbreak of a severe form of pneumonia in the South Bronx.

There have been 31 cases of Legionnaires' disease in the area since July 10, according to the city's Department of Health. Two have been fatal. Affected neighborhoods include Highbridge, Morrisania, Hunts Point and Mott Haven.

The disease is caused by a bacteria called legionella. Experts are testing water and other potential sources as they try to determine the source of the outbreak. 

The disease became widespread in Co-op City this past winter. 

Anyone with pneumonia-like symptoms, including fever, cough, chills and muscle aches, should seek medical attention, according to officials. 

The disease spreads through water droplets, but experts at St. Barnabas Hospital say that the disease cannot be spread from person to person.