Table 2. Ethnic demographics of the study population and hantavirus antibody prevalencea Ethnicity or nationality No positive/tested (%) Nativeb without specification 13/229 (5.7) Native with Bolivian lineage 6/56 (10.7) Native with Paraguayan lineage 1/7 (14.2) Native total 20/292 (6.8) Indigenous without specification 0/3 (0) Indigenous Guaraní 0/17 (0) Indigenous Chaguanco 0/1 (0) Indigenous Charagua (Bolivia) 1/1 (100) Indigenous total 1/22 (4.5) Bolivians 1/24 (4.2) Paraguayan 0/1 (0) Foreigners total 1/25 (4) Without data 0/2 (0) aBy immunoglobulin G enzyme-linked immunosorbent assay. bNative, born in Argentina. findings in relation to house location and occupation of participants. Forty persons with urban occupations includ- ed 10 administrative employees, 13 health workers, 5 housewives, 4 students, and other miscellaneous occupa- tions (technician, gardener, bricklayer, retired). Among suburban study participants, 23 were housewives, 28 were students, and the rest were employed in a variety of occu- pations (employee, health agent, maid, bricklayer). Among rural participants, 75 were agricultural workers, 64 house- wives, 29 students, 10 sawmill workers, and the rest had miscellaneous occupations (employee, trader, bricklayer, retired). All three hantavirus-antibody–positive partici- pants living in urban dwellings worked in rural areas (a bricklayer, a sawmill worker, and an agricultural worker), as did two antibody-positive participants living in subur- ban houses (agricultural workers). Thirteen (17.1%) of 76 participants with antibodies were agricultural workers (laborers, farmers, fincas owners). Antibody prevalences for other occupations included housewives (4 [6.3%] of 64), and sawmill workers (1 [10%] of 10). We found no hantavirus antibodies among 61 students or 20 healthcare workers, including physicians, nurses, health agents, and a dentist. If occupations are considered as rural (positive IgG, 20 [10%] of 201) or not rural (urban and suburban, positive IgG 1 [1.03%] of 97), hantavirus antibody prevalence is significantly higher in the former (chi square=7.95, p=0.004); among those with rural occupations, those whose employment included agricultural activities had a higher prevalence of hantavirus antibodies (positive IgG 13 [17.1%] of 76; 7 [5.6%] of 125; chi square=6.98, RESEARCH p=0.008). Table 4 shows clinical and epidemiologic data for the study population. Most (86%) hantavirus antibody–posi- tive participants did not recall previous HPS clinical man- ifestations. The presence of rodents was reported by 77% of hantavirus antibody–positive and 79% of hantavirus antibody–negative persons, both in peridomestic and workplace settings. Among persons who had previous contact with known HPS patients, 6 (6.1%) of 98 cases had hantavirus antibod- ies. Similar antibody prevalence was found in persons who did not have prior contact with a known HPS patient (16 [6.6%] of 242; chi square p>0.05). One hundred five per- sons (30.8%) reported no trips outside the area, and 58% of the remainder had traveled only to other areas inside the province or to nearby Salta Province; 41.6% reported trips to Bolivia in addition to local trips. Only a small percent- age (0.4%) had visited relatively distant areas of the coun- try. Hantavirus antibodies were found in 15 (6.4%) of 233 persons who traveled outside the immediate region, and 7 (6.6%) of 105 who had not traveled outside of the imme- diate region. Rodent Study A total of 361small mammals were captured in 2,427.5 trap-nights (overall trap success 14.8%). Captures repre- sented two rodent families, three subfamilies, and 13 species (Table 5). Calomys and Akodon were the most fre- quently trapped genera (38% and 40.2%, respectively) and the sole taxa that were found with hantavirus antibodies. Hantavirus IgG was found in 4 (2.8%) of 140 Akodon sim- ulator and 7 (5.1%) of 137 Calomys callosus. The genus Oligoryzomys has several species previously identified as hantavirus reservoirs in the three HPS-endemic areas of the country. In this study, this genus accounted for 12 (3.3%) of the 361 captures; however, none was positive for hantavirus antibody. Table 6 shows the species distribution according to the different habitats sampled. The specimens of C. callosus were trapped inside dwellings located at dif- ferent fincas. More than half (6 [54.5%] of 11) of the positive rodents were captured in weeds, roadsides, or peridomestic sites at fincas (fruit trees and vegetable plantations); four were trapped in brushwood, and the last one at the riverside very near an HPS patient’s dwelling at El Bananal. Two lines contributed with two positive rodents on each. These were located in grapefruit plantations (weeds and roadside). Table 3. Hantavirus antibody prevalence by location of residence site and location of occupational activitya Urban no. positive/tested (%) Suburban no. positive/tested (%) Rural no. positive/tested (%) Dwellings 3/31 (9.7) 4/121 (3.3) 15/189 (8) Occupational activity 0/40 (0) 1/57 (1.8) 20/201 (10) aAs determined by immunoglobulin G enzyme-linked immunosorbent assay. Emerging Infectious Diseases • Vol. 9, No. 9, September 2003 1073