A review of the world literature on the "Legionnaires' disease", an infectious disease which was designated in 1979 as "legionellosis" and described in three different clinicoanatomic forms is presented. These forms differ both in manifestations of the disease and in species of the causal agents, legionellae, united in a genus Legionellaceae. Particular attention in the review is paid to morphological lesions observed in legionelloses (macro- and microscopic, and ultrastructural). The necessity of a careful histobacterioscopic examination of tissues in suspected cases of legionellosis and additional crucial bacteriological and serological examinations is noted. Since in the majority of the observations the main pathological process was represented by pneumonia (pleuropneumonia with frequent abscessing), the main differential diagnostic features of legionellosis pneumonia and its differences from other similar infectious diseases are described.
