Bacteria responsible for many cases of Legionnaires' disease emerged only in recent decades and seem to be adapting to human environments.
Legionella pneumophila (pictured) is found in aquatic environments worldwide and can contaminate water supplies, causing outbreaks of pneumonia that can be fatal. A team led by Julian Parkhill at the Wellcome Trust Sanger Institute in Hinxton, UK, and Carmen Buchrieser at the Pasteur Institute in Paris sequenced the genomes of 337 L. pneumophila isolates belonging to 5 types that cause almost half of all cases of Legionnaires' disease in northwest Europe. Sequence analysis suggested that the 5 types emerged independently during the past few decades and spread around the world.
The recent emergence and spread of these lineages suggests that people infected with the bacterium are helping to disseminate it and that it is adapting to man-made water systems, the authors say.