The relative abundance of deer mice with antibody to Sin Nombre virus corresponds to the occurrence of hantavirus pulmonary syndrome in nearby humans.

Sin Nombre virus (SNV) is the principal cause of hantavirus pulmonary syndrome (HPS) in the United States and deer mice (Peromyscus maniculatus) are its principal rodent host, and thus the natural cycle of the virus is related to the occurrence of HPS. Prevalence of rodent infection appears to be associated with fluctuations in deer mouse populations and, indirectly, with timing and amount of precipitation, a complex of biologic events. Given that rodent population abundances fluctuate, often acutely, it is not unreasonable to assume a direct correlation between the numbers of infected rodents and the number of human infections, unless confounding factors are involved. During a 13-year longitudinal study at a site in southwestern Colorado, we accumulated data regarding deer mice and antibody to SNV and therefore had the opportunity to compare dynamics of deer mouse populations, seroprevalence of antibody to SNV in the rodents, and numbers of HPS cases in Durango and in the State of Colorado as a whole. If abundances of deer mouse populations are directly correlated with occurrence of HPS, it is reasonable to assume that low densities of deer mice and low prevalences of antibody to SNV would lead to fewer human cases than would high densities and high prevalences. Our results substantiate such an assumption and suggest that the risk of acquisition of HPS is likely related to both high numbers of infected deer mice and human activities, rather than being strictly related to prevalence of SNV in the host rodent.