Hantaviruses and their rodent reservoirs in the United States
Since 1993, three novel hantaviruses have been identified from the United States of which at least two can cause a severe respiratory disease termed hantavirus pulmonary syndrome (HPS). Rodent reservoirs have been identified for two viruses; Peromyscus maniculatus is the primary host of Muerto Canyon Virus (MCV) in the western United States and genetic analyses have implicated Sigmodon hispidus as the probable host of a hantavirus in Florida. Of 813 P. maniculatus tested in the southwestern United States 30.4% were infected; 12 of 90 (13.3 %) S. hispidus from Florida were infected. The S. hispidus-associated virus has not been isolated in cell culture and its etiologic role in human disease is unproven. The rodent reservoir for the third virus, associated with a fatal case of HPS in Louisiana, is unknown. These viruses are genetically distinct from their old world relatives, and cause a different spectrum of human disease. In the United States, respiratory disease is prominent while renal disease is most often reported from Eurasia. As yet the number of HPS cases occurring annually in the United States is unknown, but since the syndrome was identified in May, 1993, 50 cases have been reported from 15 states with an overall mortality ratio of 60%. The risk to groups occupationally exposed to rodents is being investigated.