Etiologic Agent Legionella pneumophila and other Legionella species. At least 43 species and 65 serogroups have been identified. Pontiac fever has been recognized only during outbreaks.
Pontiac fever is a self-limited disease that requires no treatment.
Transmission Inhalation of contaminated aerosols from devices such as cooling towers, showers, and faucets, and aspiration of contaminated water. The elderly, cigarette smokers, persons with chronic lung or immunocompromising disease, and persons receiving immunosuppressive drugs. Trends Increasing awareness among physicians and use of more sensitive, noninvasive tests such as urine antigen testing has led to improved recognition of sporadic cases and outbreaks caused by L. pneumophila , serogroup 1. Decreased use of culturing may be hampering recognition of infections caused by Legionella species and serogroups. Challenges Diagnosis of legionellosis requires specialized testing.