A spike in Legionnaires’ disease cases in the Milwaukee area last summer was likely caused by multiple sources, according to a new report from the Centers for Disease Control and Prevention (CDC). During a three-month period last summer, Milwaukee County reported more than twice the number of annual cases and health investigators scrambled to find the source.
Legionnaires’ disease is a severe form of pneumonia that is transmitted when water vapor contaminated with Legionella bacteria is inhaled. It can’t be transmitted from person-to-person. It got its name from a 1976 outbreak that struck an American Legion convention in Philadelphia.
A less severe form of legionella infection is called Pontiac fever. Each year, between 8,000 and 18,000 Americans are sickened by infections from Legionella, called legionellosis. Symptoms of these infections include cough, shortness of breath, fever, muscle aches and headaches.
Between June 1 and September 30, 2013, 58 laboratory-confirmed cases of Legionnaires’ disease were reported in Milwaukee County, more than twice the number of total annual cases the county usually reports. All but one person were hospitalized. Most of the cases, 78 percent, were reported in the city of Milwaukee. The case patients ranged in age from 29 to 77 years old. The median age was 53.
The Milwaukee Health Department (MHD) took environmental samples from 11 sites within the city including commercial building cooling towers; a large, outdoor water fountain; a public swimming pool/waterpark with spray features; and two residences for homebound patients. In all, 39 samples were collected. Three samples from cooling towers were positive for Legionella, but they did not match the outbreak strain.
MHD met with cooling tower consultants and contractors to address gaps in maintenance that were the result of a longer-than-average period of disuse caused by unseasonably cool June weather followed by extremely hot weather in July. Health officials determined that the cooling towers were one of several likely sources for the outbreak.
