The Isolation of Arthropod-Borne Viruses, including Members of Two Hitherto Undescribed Serological Groups, in the Amazon Region of Brazil *

Summary Arthropod-borne virus studies have been in progress for more than 4 years in a small region with tropical rain forest climate in the Belem area of the Amazon Valley. Here, 451 strains have been isolated from man (64), sentinel monkeys (221), sentinel mice (116), mosquitoes (33) and wild animals (17). These agents belong to six serological groups, two of which are new and were first identified from the Belem area. Eighteen serological types have been isolated and studied. Nine of these are recognized viruses as follows: Eastern equine encephalomyelitis, Mayaro and Venezuelan equine encephalomyelitis in group A; Ilheus and yellow fever in group B; Cache Valley, Kairi and Wyeomyia in the Bunyamwera group; and Tr 9375 in the California complex. Nine new agents were discovered: Bussuquara in group B; Apeu, Caraparu, Marituba, Murutucu and Oriboca in the new group C; Guama and Catu in the new Guama group; and one ungrouped agent, Tacaiuma (An 73).