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June 19, 1981

Legionnaires' Disease: An Epidemiologic Overview

Author Affiliations

University of Pittsburgh School of Medicine Veterans Administration Medical Center Pittsburgh

JAMA. 1981;245(23):2429. doi:10.1001/jama.1981.03310480045028

The development of any infectious disease, from an epidemiologic perspective, requires three conditions: a reservoir for the etiologic agent, a mode of transmission, and the presence of a susceptible host. The article by Band and colleagues in this issue of The Journal (p 2404) describing an outbreak of Legionnaires' disease (LD) addresses all three of these conditions. Water in an air conditioning cooling tower contaminated with Legionella pneumophila constituted the reservoir for this outbreak of LD. The mode of transmission was airborne, as convincingly demonstrated by environmental studies and epidemiologic analysis. Smoke-tracer studies showed that aerosolized exhaust from the cooling tower could be transmitted down a hotel chimney, out of a fireplace, and into a hotel meeting room. The attack rate of LD was highest for those hotel patrons occupying the meeting room with the fireplace. The susceptible host in this outbreak, as in other outbreaks of LD, was the