Various species of Legionella bacteria, frequently Legionella pneumophila, serogroup I.
Infection results from inhalation of contaminated water sprays or mists. The bacteria live in water and colonize hot-water systems at temperatures of 20–50 °C (optimal 35–46 °C). They contaminate air-conditioning cooling towers, hot-water systems, humidifiers, whirlpool spas and other watercontaining devices. There is no direct person-to-person transmission.
Nature of the disease
Legionellosis occurs in two distinct clinical forms:
- Legionnaires’ disease is an acute bacterial pneumonia with rapid onset of anorexia, malaise, myalgia, headache and rapidly rising fever, progressing to pneumonia, which may lead to respiratory failure and death.
- Pontiac fever is an influenza-like illness with spontaneous recovery after 2–5 days.
Susceptibility to legionellosis increases with age, especially among smokers and people with pre-existing chronic lung disease and those who are immunocompromised.
Risk for travellers
The risk for travellers is generally low. Outbreaks occasionally occur through dissemination of infection by contaminated water or air-conditioning systems in hotels and other facilities used by visitors.
None. Prevention of infection depends on regular cleaning and disinfection of possible sources.