This bacteria is showing up repeatedly in the U.S. and Europe. Most recently a building in Portland is infected with it.
Legionella is common in many environments, with at least 50 species and 70 serogroups identified. The side-chains of the cell wall carry the bases responsible for the somatic antigen specificity of these organisms. The chemical composition of these side chains both with respect to components as well as arrangement of the different sugars determines the nature of the somatic or O antigen determinants, which are essential means of serologically classifying many Gram-negative bacteria.
Legionella acquired its name after a July, 1976 outbreak of a then-unknown “mystery disease” sickened 221 persons, causing 34 deaths. The outbreak was first noticed among people attending a convention of the American Legion – an association of U.S. military veterans. The convention in question occurred in Philadelphia during the U.S. Bicentennial year. This epidemic among U.S. war veterans, occurring in the same city as – and within days of the 200th anniversary of – the signing of the Declaration of Independence, was widely publicized and caused great concern in the United States. On January 18, 1977 the causative agent was identified as a previously unknown bacterium, subsequently named Legionella.