Fil: Riera, Laura. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Castillo, Ernesto. Dto. Ciencias Naturales. Facultad de Ciencias Exactas, Físico Químicas y Naturales, Universidad Nacional de Río Cuarto, Córdoba; Argentina.Fil: Del Carmen Saavedra, María. . ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Priotto, José. Dto. Ciencias Naturales. Facultad de Ciencias Exactas, Físico Químicas y Naturales, Universidad Nacional de Río Cuarto, Córdoba; ArgentinaFil: Sottosanti, Josefa. . ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Fil: Polop, Jaime. Dto. Ciencias Naturales. Facultad de Ciencias Exactas, Físico Químicas y Naturales, Universidad Nacional de Río Cuarto, Córdoba; Argentina.Fil: Ambrosio, Ana María. . ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Virales Humanas; Argentina.Lymphocytic choriomeningitis virus (LCMV) is the prototype of the family Arenaviridae and is associated with the natural reservoir, Mus domesticus (Md). It causes meningitis and a flu-like illness characterized by malaise, myalgia, retrorbital headache, and photophobia. This study presents the data obtained in a rodent and human serological study during 6 years (1998-2003) in the city of Rio Cuarto, Argentina. Antibodies anti-LCMV were sought by ELISA in rodents and humans. LCMV was found only in Md species in 9.4% of animals. The results also show some seasonal, no significant variations in the prevalence of the infection. Distribution of positive mice was not modified significantly by trapping sites, sex, or age of the animals. The prevalence of LCMV positive urban residents was found to be consistently low (1-3.6%) along the study period, with overage prevalence of 3.3% and values in males (4.6%) significantly higher than in females (2.6%) (P < 0.05). Seven of 432 pregnant women were found to be LCMV positive, but the absence of LCMV antibodies in the newborns demonstrated that the mothers were infected before pregnancy. This study is the first evidence on endemic LCMV in an Argentine city located outside the endemic area of Argentine hemorrhagic fever (AHF) and described the need to study other areas and increase awareness of this viral infection.