Eastern equine encephalitis (EEE) virus (Togaviridae, Alphavirus) is a highly pathogenic mosquito-borne zoonosis that is responsible for occasional outbreaks of severe disease in humans and horses, resulting in high mortality and neurological impairment in most survivors. In the past, human disease outbreaks in the northeastern U.S. have occurred intermittently with no apparent pattern; however, during the last decade we have witnessed recurring annual emergence where EEE virus activity had been historically rare, and expansion into northern New England where the virus had been previously unknown. In the northeastern U.S., EEE virus is maintained in an enzootic cycle involving the bird-feeding mosquito, Culiseta melanura, and wild passerine (perching) birds in freshwater hardwood swamps. However, the identity of key avian species that serve as principal virus reservoir and amplification hosts has not been established. We built a mathematical model with many host species to examine the impact on pathogen transmission of vector feeding preferences, host community structure, and seasonal host and vector population changes.
As a result of the model, we identified several host species as potential key virus reservoir and amplification hosts. In particular, we observe that Wood Thrush (Hylocichla mustelina) appear to be a preferred host early in the season, and as a result act as a driving force of infection. Later in the season, other species become more prevalent and preferential for feeding, particularly the Common Grackle (Quiscalus quiscula) , which allows the disease to persist throughout the remainder of the season. The model suggests that these species may play a vital role in supporting EEE virus amplification.