From Many Hosts, One Accidental Pathogen: The Diverse Protozoan Hosts of .

The 1976 outbreak of Legionnaires' disease led to the discovery of the intracellular bacterial pathogen . Given their impact on human health, species and the mechanisms responsible for their replication within host cells are often studied in alveolar macrophages, the primary human cell type associated with disease. Despite the potential severity of individual cases of disease, are not spread from person-to-person.