Legionella Infections

Legionellosis refers to both Legionella pneumonia (legionnaires disease) and Pontiac fever. Legionella pneumonia, which can be sporadic or epidemic, can be acquired in the community or health care setting. Pontiac fever is an acute, self-limited febrile illness caused by inhalation of Legionella spp. Legionella spp. are slender, noncapsulated, nonspore-forming, aerobic, nutritionally fastidious, gram-negative bacilli that belong to the Legionellaceae family. L. pneumophila serogroup 1 is the most commonly identified species that causes human disease. Legionella spp. are facultative intracellular pathogens found worldwide in water, both in the natural environment and in man-made water systems. Disease is caused by inhalation or microaspiration of water contaminated with Legionella spp. Waterborne outbreaks due to contaminated drinking water, air conditioning systems, water cooling towers, hot tubs, and other sources continue to occur, and reported rates of Legionella pneumonia are increasing. Signs and symptoms of Legionella pneumonia are similar to other causes of community-acquired pneumonia. A high index of suspicion is required to identify risk factors, perform specific laboratory testing, and establish the diagnosis. Early appropriate empiric antibiotic therapy improves outcomes.