Naturally occurring Sin Nombre virus genetic reassortants.

Genetic reassortment has been shown to play an important role in the evolution of several segmented RNA viruses and in the epidemiology of associated diseases. Sin Nombre (SN) virus is the cause of hantavirus pulmonary syndrome throughout the western United States. Like other hantaviruses, it possesses a genome consisting of three negative-sense RNA segments, S, M, and L. Recent analysis has demonstrated the presence of at least three different hantaviruses in Nevada and eastern California, including SN, Prospect Hill-like, and El Moro Canyon-like viruses. In addition, two distinct lineages of SN virus can be found in Peromyscus maniculatus rodents (sometimes in close proximity) trapped at study sites in this region. Data obtained by phylogenetic analysis of sequence differences detected among the S, M, and L genome segments of these SN viruses are consistent with reassortment having taken place between SN virus genetic variants. The results suggest that M (and to a lesser extent S or L) genome segment flow occurs within SN virus populations in P. maniculatus in this region. No reassortment was detected between SN virus and other hantavirus types present in the area. This finding suggests that as genetic distance increases, the frequency of formation of viable reassortants decreases, or that hantaviruses which are primarily maintained in different rodent hosts rarely have the opportunity to genetically interact.