What is Legionellosis?

Legionellosis (or legionnaires' disease) is a lung infection caused by the bacterium Legionella spp. The infection occurs by inhalation of aerosolized contaminated water in sufficiently fine particles capable of penetrating until reaching the pulmonary alveoli. In fact, no cases were found following the ingestion of contaminated water and no type of transmission from person to person.

Legionellosis can occur in the following clinical cases:

• Subclinical form, asymptomatic.
• Pontiac fever: flu-like form.
• Legionnaires' disease: it is the most severe form of the infection, with an average lethality of 10%.
• Extrapulmonary leginellosis.

The incidence of legionellosis depends on the:

• degree of water contamination.
• immunological susceptibility of the exposed population (e.g. the hospital population).
• intensity of exposure.
• availability of diagnostic tests.