Sin Nombre Virus | Ask Microbiology

Sin Nombre virus is a member of the genus Orthohantavirus (family Hantaviridae) and the principal etiological agent of hantavirus pulmonary syndrome (HPS) in North America. This enveloped virus has a tri‑segmented negative‑sense RNA genome (S, M and L) encoding the nucleocapsid protein, glycoproteins Gn and Gc, and RNA‑dependent RNA polymerase. The name means “no name” in Spanish, chosen to avoid stigmatizing geographic labels after its discovery in 1993 during an outbreak in the Four Corners region of the United States.

Genomic Features, Ecology and Pathogenesis

Within the New World hantavirus clade, Sin Nombre virus is phylogenetically related to other Peromyscus‑borne viruses such as New York virus and Monongahela virus. Its natural reservoir is the deer mouse (Peromyscus maniculatus), a common rodent throughout much of North America. The virus persists in deer mice through chronic infection and is shed in urine, faeces and saliva. Humans become infected by inhaling aerosolized excreta or, rarely, through bites. After inhalation, Sin Nombre virus infects endothelial cells, leading to increased vascular permeability and a rapid onset of fever, myalgia and cough that can progress to non‑cardiogenic pulmonary oedema and shock. The case fatality rate of HPS caused by Sin Nombre virus is approximately 30–40 %, and there is no evidence of human‑to‑human transmission.

Outbreaks and Public Health Impact

The virus came to prominence during the 1993 outbreak of unexplained respiratory illness in the Four Corners area of New Mexico, Arizona, Colorado and Utah that resulted in dozens of cases and high mortality. Subsequent investigations identified the deer mouse reservoir and led to broader recognition of hantavirus pulmonary syndrome in North America. Sporadic cases have since been reported across the United States, Canada and parts of Mexico, often associated with exposure to rodent‑infested cabins, barns or recreational areas. A notable cluster occurred in 2012 among visitors to Yosemite National Park who stayed in rodent‑infested tent cabins. There is no approved vaccine; treatment focuses on early recognition, intensive supportive care and careful fluid management. Public health measures emphasize rodent control around homes and education about avoiding exposure to deer mouse excreta.

Sin Nombre virus remains an important cause of severe rodent‑borne disease in North America. Because of its high fatality and rapid progression, prompt diagnosis and supportive therapy are critical. Preventing human infection relies on controlling deer mouse populations and minimising contact with their habitats.