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August 12, 1996

Risk Factors for Domestic Acquisition of Legionnaires Disease

Author Affiliations

Ohio Legionnaires Disease Group

From the Division of Bacterial and Mycotic Infections, National Center for Infectious Dieseases, Centers for Disease Control and Prevention, Atlanta, Ga (Drs Straus, Lipman, and Breiman and Mr Benson); Department of Medicine, University of North Carolina, Chapel Hill (Dr Straus); Department of Medicine, Ohio State University, Columbus (Dr Plouffe and Ms Hackman); and the Department of Medicine, Northeastern Ohio Universities College of Medicine, Akron (Dr File and Ms Salstrom). Members of the Ohio Legionnaires Disease Group are listed in a box on page 1688.

Arch Intern Med. 1996;156(15):1685-1692. doi:10.1001/archinte.1996.00440140115011

Background:  Legionnaires disease is a common cause of adult pneumonia. Outbreaks of legionnaires disease have been well described, but little is known about sporadically occurring legionnaires disease, which accounts for most infections. Exposure to contaminated residential water sources is 1 plausible means of disease acquisition.

Methods:  Employing a matched case-control study design in 15 hospitals in 2 Ohio counties, we prospectively enrolled 146 adults diagnosed as having nonepidemic, 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 followed by a home survey that included sampling residential sources for Legionella. Interview and home survey data were analyzed to estimate the risk of acquiring legionnaires disease associated with various exposures.

Results:  Multivariate analysis showed that a nonmunicipal water supply (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), and 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 than 40 hours weekly (OR, 2.13; 95% CI, 1.12-4.07), and spending nights away from home before illness (OR, 1.68; 95% CI, 1.03-2.74) were additional possible risk factors. Lower chlorine concentrations in potable water and lower water heater temperatures were associated with residential Legionella colonization.

Conclusions:  A proportion of sporadic cases of legionnaires disease may be residentially acquired and are associated with domestic potable water and disruptions in residential plumbing systems. Potential strategies to reduce legionnaires disease risk include consistent chlorination of potable water, increasing water heater temperatures, and limiting exposure to aerosols after domestic plumbing repairs.Arch Intern Med. 1996;156:1685-1692