Pichindé, a new Tacaribe-group virus, is described from Colombia. Its group relation was established by complement-fixation (CF) test with a Tacaribe-group immune fluid; its distinctness from other Tacaribe-group viruses was determined by CF and plaqueneutralization tests. The virus is biologically similar to some other members of the group with respect to behavior in infant mice and hamsters, prolonged viremia in the natural host, and the difficulty in demonstrating neutralizing antibodies in immune fluids in which CF antibodies are present. All isolations from vertebrates have been made from the cricetine rodent Oryzomys albigularis, except for one from Thomasomys fuscatus. In the Pichindé valley, virus was detected in O. albigularis at all times of year during the period 1965–69, and the mean isolation rate was 20%. Virus also was recovered from O. albigularis at localities 100 km south and 400 km north of the Pichindé valley. On several occasions the virus was isolated from mites, Gigantolaelaps, and ticks, Ixodes tropicalis, derived from viremic O. albigularis. Two of 82 serum specimens from persons living or working in close association with habitats of infected rodents reacted by CF test with Pichindé virus antigen.
Present address: Department of Tropical Medicine, Louisiana State University Medical Center, 1542 Tulane Avenue, New Orleans, Louisiana 70112.