Prevalence of antibody to serogroups 1-4 of Legionella pneumophila: a seroepidemiologic study using the indirect hemagglutination test.

An indirect hemagglutination test was used to determine the prevalence of antibody to serogroups 1-4 of Legionella pneumophila in sera from 1200 apparently healthy Michigan residents. Serogroup 1 was the most prevalent; 71 (11.8%) of 600 sera collected during the winter months (January-April, 1980) and 131 (21.8%) of 600 sera collected during the summer period (July-September, 1980) had serogroup 1 titers. This seasonal difference was independent of sex and was statistically significant in four of six age groups studied. A trend toward decreasing prevalence in the 50-59 years and 60 years or older age groups was noted in the winter sample and was statistically significant in the summer study. Prevalence of antibody to serogroups 2, 3, and 4 was significantly lower, and was associated with serogroup 1 reactivity.