Association of Shower Use With Legionnaires' Disease

OUTBREAKS of legionnaires' disease (LD) have been linked to aerosols from evaporative condensers and cooling towers,1,2whirlpool spas,3respiratory therapy equipment,4and humidifiers.5An association between shower use and LD has been hypothesized but not epidemiologically demonstrated.6-11Prevention of LD is limited by a lack of understanding of the ecology ofLegionella pneumophila. Monitoring aerosolproducing sites forL pneumophilacan be misleading since the bacteria are found often in water sources without a known disease association.12 Factors essential forLegionellamultiplication in water are poorly understood, but the bacteria multiply extracellularly on supplemented culture media.13,14Nutritional requirements of the genus are unlikely to be met in most water sources; however, these bacteria do multiply inside protozoa,15-17which are common to aquatic environments.Legionella pneumophilagrows in water samples with amoebae but not in those without viable amoebae.17Recognition of the association