Legionellosis: ecological factors of an environmentally 'new' disease.

This review paper discusses environmental factors influencing multiplication, persistence and virulence of Legionella. The differing modes of transmission of legionellosis are discussed in relation to the epidemiology and clinical manifestations of the disease. Characteristics of pathogenicity of Legionella are compared to other pathogens. Implications for prevention are presented, and areas where further research is needed are discussed.