Sin Nombre virus (SNV), an emerging pathogen in the United States, was identified in 1993. This hantavirus, a member of the Bunyaviridae family of RNA viruses, is transmitted by its reservoir host Peromyscus maniculatus, the deer mouse. Transmission is by inhalation of aerosolized feces, urine, or saliva from the infected mice. The illness that pursues, hantavirus pulmonary syndrome (HPS), is characterized initially by mild flu-like symptoms, followed by rapid progression to respiratory distress. There is no established therapeutic regimen and treatment is only supportive. Preventive methods include attempts to minimize contact with the rodents since elimination of the virus is not realistic.