A growing body of work demonstrates that loss of biodiversity negatively impacts ecosystem functions. One function, or service, that biodiverse ecosystems provide is suppression of zoonotic diseases, which are defined as diseases carried by wildlife hosts that can spill over into human populations. Ebola, SARS, West Nile virus, Hantavirus, Avian Influenza and Lyme disease are just a few of the recently emerging zoonotic diseases. Disease suppression has been shown for Lyme disease by the dilution effect, whereby increasing species diversity decreases disease prevalence in the host populations. But does a dilution effect apply to other disease systems? To test this hypothesis in a Hantavirus framework, web-sampling grids were placed in five natural areas in and around Portland, Oregon, using 352 live-traps of four different trap types. Each trapping event lasted four nights and each park was trapped nineteen times over the course of three years. Biodiversity was calculated with a Simpson's Index. Deer mouse densities and 15 vegetative characteristics were also measured. Blood samples from captured animals were tested for hantaviral antibodies using ELISA. In all, 5061 specimens from 21 species were captured, of which 3175 were Peromyscus maniculatus, the natural host of Sin Nombre Virus (SNV), the Hantavirus of primary human health concern in North America. The use of four trap types allowed examination of which trap, or combination of traps, yielded the best overall estimate of biodiversity, and also to test the efficacy of a rain shield used in an attempt to decrease capture mortality. SNV-positive P. maniculatus were found in all parks and allowed examination of host-viral dynamics. Additionally, this research revealed that increased levels of mammal species diversity decreased the amount of SNV in the host population. No other ecological variable considered in this study, alone or in combination, predicted the amount of Hantavirus in an ecosystem. By suppressing zoonotic disease, biodiversity provides a service that directly and positively affects human health and wellbeing. In turn, these results could be a useful tool in helping to strengthen conservation efforts. The possible mechanisms behind the relationship between biodiversity and zoonotic diseases will also be discussed.