using RNA extracted from autopsy material as well as RNA extracted from cell culture-adapted virus. The L RNA is 6562 nucleotides (nt) in length; the M RNA is 3696 nt long; and the S RNA is 2059 to 2060 nt long. When the prototype sequence (NMH15) of SNV detected in tissues from an HPS case was compared with the sequence of the SNV isolate (NMR11; isolated in Vero E6 cells from Peromyscus maniculatus trapped in the residence of the same case), only 16 nucleotide changes were found, and none of these changes resulted in alterations in amino acid sequences of viral proteins. It had been assumed that in the process of adaptation to cell culture, selection of SNV variants which grow optimally in cell culture would occur, and selected variants would differ genetically from the parental virus. Though NMH10 and NMR11 are identical in protein sequence, nucleotide substitutions in nontranslated regions of the genome could be responsible for altered viral phenotypes, as could changes in protein glycosylation or virus membrane components. The nested RT-PCR assay developed during the initial HCPS outbreak provided a rapid method for the genetic characterization of novel hantaviruses that did not require a virus isolate. Numerous new hantaviruses have been detected by RT-PCR in rodent tissues but have yet to be associated with human disease. These include El Moro Canyon virus associated with the western harvest mouse, Reithrodontomys megalotis, Tula virus with Microtus arvalis and M. rossiaemeridionalis, Rio Segundo virus with the Mexican harvest mouse, R. mexicanus, Isla Vista virus with the California vole, M. californicus, and Prospect Hill-like viruses in Microtus species. See also 1993 Four Corners hantavirus outbreak Hantavirus References External links Virology - CDC Hantaviruses Clinical and Lab Recognition and other info Viral diseases Hantaviridae Viral respiratory tract infections