PATTERNS OF ASSOCIATION WITH HOST AND HABITAT - ANTIBODY-REACTIVE WITH SIN-NOMBRE-VIRUS IN SMALL MAMMALS IN THE MAJOR BIOTIC COMMUNITIES OFTHE SOUTHWESTERN UNITED-STATES

The distribution and prevalence of antibody reactive with Sin Nombre v irus were determined in mammals in biotic communities of the southwest ern United States. Small mammals (n = 3,069) of 69 species were trappe d in nine communities from lower Sonoran desert to alpine tundra. Anti body was found in rodents from all communities (overall prevalence = 6 .3%); prevalence was lowest at the altitudinal and climatic extremes ( 0.4% in desert and 2.0% in alpine tundra). Antibody occurred in 11% of 928 deer mice, 20% of 355 brush mice, 23% of 35 western harvest mice, and 12% of 24 Mexican voles. No infected deer mice were found in dese rt habitat; prevalence varied from 4% in chaparral to 17% in pinyon-ju niper. Brush mice were frequently infected in chaparral and montane fo rest (25%). Seropositivity was higher in males and in heavier animals, suggesting horizontal transmission among adult males. Decreasing prev alence with age among the youngest deer mice suggests that infected da ms confer passive immunity to pups.