COMMUNITY OUTBREAK OF LEGIONNAIRES-DISEASE - AN INVESTIGATION CONFIRMING THE POTENTIAL FOR COOLING-TOWERS TO TRANSMIT LEGIONELLA SPECIES

In August and September 1993, we investigated an outbreak of legionnai res' disease in Fall River, Massachusetts, that involved 11 persons; t he attack rate was highest in Flint, a community of Fall River, All ca ses were infected with Legionella pneumophila serogroup 1 (Lp-l), A ca se-control study revealed that cases were more likely than matched con trols to have visited sites in neighborhood A of Flint. Environmental sampling in Flint found that four of nine aerosol-producing devices sa mpled contained legionellae; only two, conjoined cooling towers on bui lding A, contained Lp-l. Three independent methods of subtyping-monocl onal antibody subtyping, arbitrary primer polymerase chain reaction, a nd pulsed-field gel electrophoresis-revealed that Lp-l isolates from t hree cases with culture-positive legionnaires' disease matched those f rom the cooling towers on building A. Water samples from the homes of cases with culture-positive legionnaires' disease contained no legione llae. The results of this epidemiologic and laboratory investigation i ndicate that the cooling towers on budding A were the source of the ou tbreak of legionnaires' disease and confirm the importance of cooling towers in the transmission of legionnaires' disease.