In 1976 there was an outbreak of an unusual “atypical” pneumonia among attendees at an American Legion Convention in Philadelphia at the Bellevue Stratford Hotel. Investigation determined that it was a gram-negative bacterium from water vapor exuded from the water cooling towers that provided air conditioning. They named it Legionella Pneumophila. A later outbreak in Pontiac, Michigan yielded a less severe form, Pontiac Fever.
Summer and autumn are the most common seasons for Legionnaire’s. The bug lives in fresh water, contaminating water tanks, hot tubs, and cooling towers of large air conditioners, which is why apartment buildings and hotels are often the source of these outbreaks. Contaminated vapor-mist spreads for several thousand feet. It does not spread person to person. Many who inhale the organism have no response or mild symptoms attributed to a “cold.” Risk factors: older age, smoking history, chronic disease, and drug or disease causes of immune dysfunction. Death from respiratory failure occurs in about 10% of previously healthy patients and 25% of those with risk factors.
Symptoms develop from 2-10 days (and up to 20 days) after inhalation: fever, chills, dry or wet (possibly bloody) cough, muscle ache, headaches, tiredness, appetite loss, gait discoordination, chest pain, diarrhea, and vomiting. About 50% have GI symptoms and 50% have neurological symptoms. A slow heart rate with fever is a clue. Diagnosis: urine antigen test (30% false negative rate) or sputum culture.
There is no vaccine; prevention relies on regular water system maintenance. Antibiotics are effective. New York State requires testing, inspection and compliance before starting AC and every 90 days thereafter.
