Table 6. Distribution of rodent species by capture habitat Districts Domestica Peridomesticb 5 Species Domestica Akodon simulator Akodon sp Akodon caenosus Calomys callosus 8 5 25 Holochilus chacarius Mus musculus 7 3 Oligoryzomys sp Oligoryzomys chacoensis O. longicaudatus Oxymycterus paramensis 1 Rattus rattus 1 4 1 Thylamys elegans T. venustus 1 No identification 1 Total 7 20 9 33 aInside households. bImmediate vicinity of houses, including yards, outbuildings, vegetable gardens, weeds, fence lines, and railroad. cIncludes grapefruit and banana plantations, vegetables cultivation, weeds, and roadside in the same sites. dSeminatural habitat that includes a streamside. Habitat Farms Peridomesticb 7 Cultivationc 51 44 7 2 1 1 17 123 Brushwoodd 77 2 3 55 4 4 6 2 16 169 RESEARCH Total 140 2 3 137 11 10 2 4 6 3 6 1 2 34 361 observed in the survey and predominance of males among patients. A high antibody prevalence has been previously found in indigenous communities of the Gran Chaco of Paraguay (40.4%) and Argentina (17.1%) (in Salta Province). In those studies, the aboriginals evaluated belong to closed communities that still fish, hunt, and gather for their suste- nance. Their main ethnic groups are Chorote, Chulupi, and Wichi of the Mataco-Mataguayan linguistic family (5). In the area in our study, aboriginal and foreign people are in the minority (14% in the sample). Indigenous people (22 in this sample) belong to different groups; 77% are Guaranies from Paraguay. Only one person from the Charagua com- munity, which originated in Bolivia, participated in the study. This person had hantavirus antibodies. Among the 25 foreign participants, the only antibody-positive person belonged to the Bolivian majority (14). All nonnative inhabitants, including those with aboriginal ancestors and foreigners, are integrated members of the general popula- tion, sharing jobs and household conditions with local peo- ple, and therefore sharing similar risk factors. More than two thirds of the studied group had traveled inside or outside the province, and/or to Bolivia. Such trips are frequent among migrant farm laborers, who follow har- vest seasons. No differences were found in the antibody prevalence between persons who traveled and those who did not, probably because the reported trips were primari- ly within the same ecologic area. The genetic diversity of sigmodontine rodents in South America is well known (15). Characterization of rodent species and their association with indigenous hantaviruses are currently under study. Putative rodent reservoirs of pathogenic hantaviruses identified in Argentina thus far belong to the Oligoryzomys genus (O. longicaudatus for Andes and Oran genotypes, O. chacoensis for Bermejo genotype, and O. flavescens for Lechiguanas genotype). Three previous rodent expeditions were performed in the northwestern Argentine hantavirus-endemic area in rela- tion to HPS studies: two in Salta Province (July 1995 and October 1996) and one in Jujuy Province (May 1998), involving the villages of La Mendieta and Libertador General San Martin. Hantavirus antibody–positive species from Salta included O. chacoensis (1 [3.7%] of 27), A. simulator (1 [3.8%] of 26), and O. longicaudatus (2 [7.7%] of 26) and in Jujuy O. chacoensis, (1 [8.3%] of 12) (16). In the present study, hantavirus antibody prevalence among rodents was similar to that previously reported in the country (2.7% to 12.5 %, varying by area and species) (16), but the species found with hantavirus antibodies were different. The genera of hantavirus antibody–positive rodents corresponded to those with higher relative abun- dance, Akodon and Calomys. Akodon, associated with the Pergamino virus in central Argentina, has thus far not been reported to be pathogenic for humans (17). Among the species of Calomys, C. laucha has been identified as the reservoir of Laguna Negra virus in Paraguay, but no previ- ous evidence suggests it circulated in Argentina (14). Sigmodontine rodents were collected in every rural habitat in which we used traps, including inside dwellings, perido- mestic sites, weeds close to grapefruit and banana planta- tions, vegetable fields, and mainly natural habitats such as woodbrush and the sides of rivers and streams. Most posi- Emerging Infectious Diseases • Vol. 9, No. 9, September 2003 1075