The entire genetic structure of the Sin Nombre virus was determined, and diagnostic tests were created. The same methods are being used in attempts to develop a vaccine. The primary host of Sin Nombre virus in the southwestern United States is the deer mouse, Peromyscus maniculatus. Sin Nombre virus, like other hantaviruses, does not cause disease in its rodent hosts. The virus is shed in the saliva, urine, and feces of these animals for many weeks and perhaps for the lifetime of the animal.
Human infection occurs when dust containing infected dried rodent excretions is inhaled.
Sin Nombre and the other newly discovered hantaviruses probably have long been present in the region of the western United States inhabited by deer mice. The virus was recognized in 1993 only because of the number and clustering of human cases, after two particularly wet winters and an abundant supply of rodent food caused an increase in rodent populations, which then led to a rise in the incidence of the disease. The risk of infection by hantaviruses can be reduced by preventing rodents from living in or near human dwellings. Rodent nests and droppings should be wetted down with a disinfectant before they are removed. See an outline for this article.