[Clinical picture of Legionnaires' disease (author's transl)]

Legionella infections can take the clinical course of a relatively harmless respiratory infection. However, serious, atypical pneumonia is a more frequent manifestation of infection with these pathogens. As yet, six different Legionella species can be identified; Legionella pneumophila appears to be the most common. Legionnaires' pneumonia is being found with increasing regularity during summer and autumn in elderly male patients with previous illnesses. The clinical picture is characterised by viral "prodrome", high fever, a dry cough, breast pain, confusion, diarrhoea, haematuria, moderate leukocytosis with lymphopenia, low concentrations of sodium in the serum and negative results from microbiological analysis of the sputum and pleural exudate. Diagnosis is confirmed culturally, microscopically and serologically; the indirect immunofluorescence test is of particular value for this purpose. Erythromycin alone or in combination with rifampicin is the treatment of choice.