“The bacterium L. pneumophila was first identified in 1977, as the cause of an outbreak of severe pneumonia in a convention centre in the USA in 1976.  Legionnaires’ disease has an incubation period of 2 to 10 days (but up to 16 days has been recorded in some outbreaks).  Untreated Legionnaires’ disease usually worsens during the first week.Of the reported cases 75–80% are over 50 years and 60–70% are male.”

World Health Organization – WHO