RISK-FACTORS FOR DOMESTIC ACQUISITION OF LEGIONNAIRES-DISEASE

Background: Legionnaires disease is a common cause of adult pneumonia. Outbreaks of legionnaires disease have been well described, but littl e is known about sporadically occurring legionnaires disease, which ac counts for most infections. Exposure to contaminated residential water sources is 1 plausible means of disease acquisition. Methods: Employi ng a matched case-control study design in 15 hospitals in 2 Ohio count ies, we prospectively enrolled 146 adults diagnosed as having nonepide mic, community-acquired legionnaires disease and compared each with 2 hospital-based control patients, matched for age, sex, and underlying illness category. An interview regarding potential exposures was follo wed by a home survey that included sampling residential sources for Le gionella. Interview and home survey data were analyzed to estimate the risk of acquiring legionnaires disease associated with various exposu res. Results: Multivariate analysis showed that a nonmunicipal water s upply (odds ratio [OR], 2.26; 95% confidence interval [CI], 1.17-4.37) , recent residential plumbing repair (OR, 2.39; 95% CI, 1.10-5.18), an d smoking (OR, 3.48; 95% CI, 2.09-5.79) were independent risk factors for legionnaires disease. Univariate analysis suggested that electric (vs gas) water heaters (OR, 1.97; 95% CI, 1.10-3.52), working more tha n 40 hours weekly (OR, 2.13; 95% CI, 1.12-4.07), and spending nights a way from home before illness (OR, 1.68; 95% CI, 1.03-2.74) were additi onal possible risk factors. Lower chlorine concentrations in potable w ater and lower water heater temperatures were associated with resident ial Legionella colonization. Conclusions: A proportion of sporadic cas es of legionnaires disease may be residentially acquired and are assoc iated with domestic potable water and disruptions in residential plumb ing systems. Potential strategies to reduce legionnaires disease risk include consistent chlorination of potable water, increasing water hea ter temperatures, and limiting exposure to aerosols after domestic plu mbing repairs.