Sin Nombre orthohantavirus (SNV) (from Spanish, meaning "without a name") is the prototypical etiologic agent of hantavirus cardiopulmonary syndrome (HCPS). Discovered in 1993 near the Cañon de la Muerte on the Navajo Reservation, it was originally named the Muerto Canyon hantavirus, in keeping with the convention for naming new pathogens. However, the Navajo Nation objected to the name in 1994. It was also near the Four Corners point in the United States, so the virologists then tried naming it the "Four Corners virus". The name was changed after local residents raised objections. In frustration, the virologists changed it to Sin Nombre, meaning "without a name" in Spanish. History It was first isolated in 1993 from rodents collected near the home of one of the initial patients with hantavirus pulmonary syndrome (HPS) in the Four Corners region of the western United States. Isolation was achieved through a blind passage in Peromyscus maniculatus (deer mouse) and subsequent adaptation to growth in Vero E6 cells. Additional viral strains have also been isolated from P. maniculatus associated with a fatal case in California and P. leucopus from the vicinity of probable infection of a New York case. Black Creek Canal virus was isolated from S. hispidus collected near the residence of a human case in Dade County, Florida. Another etiologic agent of HCPS, Bayou virus, was first isolated from the vicinity of Monroe, Louisiana. Epidemiology SNV occurs wherever its reservoir rodent carrier, the deer mouse Peromyscus maniculatus, is found, which includes essentially the entire populated area of North America, except for the far southeastern region from eastern Texas through Florida, Alaska, and the far northern reaches of Canada. SNV and HCPS are especially common in western states; peak incidences for HCPS have been reported in regions in which there is a lot of contact between humans and mice (New Mexico, Arizona) and in states with exceptionally large rural populations such as California. All of the western provinces of Canada have also reported cases. SNV can be contracted through the inhalation of virus-contaminated deer mouse excreta. The case fatality ratio of SNV-induced HCPS in the USA was reported to be about 66.7% (CDC, 1993). However, since that time the case fatality ratio has steadily declined as more mild cases came to be recognized. By 2007 the CFR had declined to about 35%. Virus sequencing The entire genomic sequence of SNV has subsequently been determined by