Despite the fact that rodents are considered to be the infectious source of hantavirus for humans, another route of transmission was demonstrated. Andes virus (ANDV) has been responsible for most of the cases recorded in Argentina. Person-to-person transmission of ANDV Sout lineage was described during an outbreak of hantavirus pulmonary syndrome in southwest Argentina. In this study, we analyzed 4 clusters that occurred in 2 disease-endemic areas for different ANDV lineages. We found new evidence of interhuman transmission for ANDV Sout lineage and described the first event in which another lineage, ANDV Cent BsAs, was implicated in this mechanism of transmission. On the basis of epidemiologic and genetic data, we concluded that person-to-person spread of the virus likely took place during the prodromal phase or shortly after it ended, since close and prolonged contact occurred in the events analyzed here, and the incubation period was 15–24 days.

We report a large case series of hantavirus pulmonary syndrome (HPS) in Argentina that was confirmed by laboratory restuls from 1995 through 2008. The geographic and temporal distribution of cases by age, sex, fatality rate, and risk factors for HPS was analyzed. A total of 710 cases were unequally distributed among 4 of the 5 Argentine regions. Different case-fatality rates were observed for each affected region, with a maximum rate of 40.5%. The male-to-female ratio for HPS case-patients was 3.7:1.0; the case-fatality rate was significantly higher for women. Agriculture-associated activities were most commonly reported as potential risk factors, especially among men of working age. Although HPS cases occurred predominantly in isolation, we identified 15 clusters in which strong relationships were observed between members, which suggests ongoing but limited person-to-person transmission.

Person-to-Person Transmission of Andes Virus

Following the occurrence of the first laboratory-confirmed cases of hantavirus pulmonary syndrome (HPS) in Maranhão State, Brazil, rodents were trapped and rodent materials screened by ELISA for antibodies to Sin Nombre and Andes hantaviruses. Antibody-positive samples were tested by RT-PCR, amplified products were sequenced, and phylogenetic trees were constructed for comparison with known hantaviruses. From 104 rodent blood samples collected (40 Bolomys lasiurus, 52 Holochilus sciureus, 12 Oligoryzomys fornesi, and one Proechimys guyannensis), 21 (20.2%) were antibody-positive (one B. lasiurus, five O. fornesi, and 15 H. sciureus). Hantavirus RNA was amplified by PCR from two O. fornesi and four H. sciureus. Viral sequencing identified two hantavirus genotypes. The genotype recovered from O. fornesi, is designated herein as Anajatuba (ANAJ) and the genotype recovered from H. sciureus is designated Rio Mearim (RIME). Phylogenetic analysis of a 643-nucleotide region of the N segment showed both viruses to be most closely related (94–96% nucleotide homology) to Río Mamoré virus, a virus associated with Oligoryzomys microtis in Bolivia and Peru, but not found in northern Brazil. O. fornesi was frequently captured in and around human dwellings. H. sciureus, is a semi-aquatic rodent captured only in remote areas rarely frequented by humans. Vector-Borne Zoonotic Dis. 5, 11–19.