Ecology
Four rodent groups carry most of the U.S. hantavirus signal, and each is associated with a specific virus and region. Knowing which rodent is dominant where you are is what makes prevention and exposure history actually meaningful.
Key facts
Each group is the primary reservoir for at least one human-pathogenic hantavirus in the United States.
The map of confirmed U.S. cases closely tracks reservoir range. Western HPS is overwhelmingly deer-mouse country; southeastern HPS picks up cotton rat and rice rat virus pairings; the white-footed mouse covers a wide eastern and central swath where lower cumulative counts are recorded.
Sin Nombre is the virus responsible for the majority of U.S. HPS cases. Its host, the deer mouse, is one of the most widely distributed rodents in North America. Sin Nombre is the virus most U.S. clinicians have in mind when they say 'hantavirus.'
The non-Sin Nombre U.S. hantaviruses are less common but documented.
Reservoir presence is not the same as transmission risk. Most rodents in a population are not actively infected, and not every encounter with rodent material produces human exposure. The probability is conditional on what people actually do in the environment.
Visually distinguishing deer mice from white-footed mice in the field is not always reliable. For prevention purposes, identification is rarely necessary — the cleanup and exclusion steps are the same regardless of species.
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