Introduction: Hantavirus cardiopulmonary syndrome (HCPS) is rare in Northeastern Brazil.
Methods: Prospective surveillance was conducted over a two-year period in Alagoas State, Northeastern Brazil. The prevalence of anti-hantavirus N-antigen IgM and IgG in human serum samples was determined by enzyme-linked immunosorbent assay testing.
Results: High avidity IgG was found in nine of 476 serum samples tested (from 102 patients with clinical manifestations compatible with HCPS, 124 patients with leptospirosis, and 250 healthy rural workers).
Conclusions: Serologic evidence of past hantavirus infection in residents of Alagoas State indicates that hantaviruses are present in northeastern Brazil, even in areas silent for HCPS.