University of Maryland • Safety Fact Sheet • Department of Environmental Safety

Legionellosis Fact Sheet

Legionellosis is a disease caused by the Legionella pneumophila bacteria. The disease has two forms; the more serious form produced a pneumonia infection more commonly known as Legionnaires' Disease. It acquired its name from an outbreak occurring at a 1976 American Legion convention in Philadelphia.

The Centers for Disease Control estimate that up to 25,000 people in the United States contract Legionnaires' Disease every year. An unknown number of infected people show mild or no symptoms at all. The disease most often affects middle-aged or older men, particularly those who smoke or drink heavily. Human infections are caused by inhalation of aerosols containing high numbers of bacteria. Infected people do not transmit the disease to others. Ingestion of the bacteria does not cause infection. Outbreaks of the disease receive significant media attention, but typically only single isolated cases are identified. Approximately 5% - 30% of people with Legionnaires' Disease die.

Symptoms of the disease appear 2 - 10 days following infection. Initial symptoms are similar to influenza - loss of appetite, tiredness, body aches and headache. Chills and a rapidly rising fever are usually apparent within 24 hours. Pneumonia develops and kidney function may be affected. Diagnosis of the disease requires identification of the bacteria in the sputum and corresponding antigen levels in the blood or urine. Physicians treat the disease with a prescribed antibiotic regimen.

The Legionella bacterium causing this disease is commonly found in the environment in creeks, ponds and soil at excavation sites. It has also occasionally been isolated in drinking water, hot water tanks, cooling towers and evaporative condensers. The bacteria grows best in warm (90° - 105° F) stagnant water. Because the organism is so common in the environment, testing for its presence is almost always limited to situations where outbreaks are suspected. Outbreaks have occurred after people have inhaled mists from cooling towers, whirlpool spas and showers.

The University of Maryland recognizes the devastating effects that can be caused by Legionella pneumophila. For this reason, several preventative measures are taken to minimize the potential for exposure to the University community:

Cooling towers are regularly cleaned and treated with biocides that inhibit or prevent the growth of Legionella or other potentially-harmful bacteria,
Air conditioning drip pans are periodically inspected for adequate drainage, and slow-release antimicrobial devices are used in the cooling season,
Any water infiltration is promptly removed and biocides applied, and
Hot water tanks are maintained at temperatures over 122°F to prevent bacterial growth.

University Resources

The Department of Environmental Safety, University Health Center and Facilities Management provide investigation and remediation services related to known or suspected Legionella infections or contaminations. For more information, please call:

University Health Center ((301) 314-8184)
   (Treatment or health-related questions)
Facilities Management Work Control Center ((301) 405-2222)
   (Removal of water, maintenance of facilities)
Environmental Safety ((301) 405-3960)
   (Assessment of Legionella hazards)

Written 8/00
Reviewed 4/05

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