[The bacteriological and immunological diagnosis of Legionnaires' disease].

There has been very rapid progress in knowledge concerning Legionnaires' disease and the Legionella. Relatively simple and reliable diagnostic techniques are already available. Isolation of Legionella is now possible as a result of the development of sensitive and specific culture media. Detection of the organism in pathological material by direct immunofluorescence leads to emergency confirmation of the diagnosis in approximately 50% of cases. Finally, serology using a specific antigen often leads to a suspicion of Legionnaires' disease a few days after its clinical onset. It provides late confirmation in the immense majority of cases. These three techniques will no doubt be followed by others which will further facilitate the recognition of Legionnaires' disease, a not uncommon and grave illness.