Guaroa virus, a new agent isolated in Colombia, South America.

Abstract

Summary A virus was isolated from the blood of 6 out of 119 persons living in Guaroa, eastern Columbia. The locality is a recent settement situated at the edge of a natural savannah in the vicinity of a stretch of tropical rain forest. There is evidence that the agent isolated was the same in five of these persons. Serological studies showed that this agent was not identical with any of the 36 different anthropod-borne viruses with which it was compared, nor, in view of the known cross relationships among members of a group, could any evidence be found indicating that the virus belongs in groups A, B, or C. Our serological studies indicate that the virus is not related to Anopheles A, Anopheles B, and Wyeomyia. The conclusion derived from the immunological studies indicated that this was a new agent, to which the name Guaroa was given. A distant relationship was found between Guaroa and California encephalitis virus; this very slight overlap was detected by HI, but not by CF, and in one direction only. Although California immune sera inhibited a Guaroa antigen, Guaroa sera failed to inhibit a California antigen. Additional studies are clearly indicated to elucidate this crossing. Guaroa virus is pathogenic for white mice, regardless of age, when inoculated by the intracerebral route. When the subcutaneous route is used, it produces fatal infections in baby mice, but not in adults. Two rhesus monkeys inoculated subcutaneously and intradermally with the human sera from which the viruses were isolated, showed viremia and immunological conversion, but none developed fever or any clinical disease. Guaroa virus was isolated from persons who, at the time of the bleeding, did not complain of being sick. Four of these individuals apparently continued to enjoy good health during the month following the isolation of the virus. One person had a mild febrile illness lasting two days which started on the second day after the bleeding. It was not possible to continue the study of the sixth individual. A large proportion of residents of Guaroa was found to have neutralizing antibodies for Guaroa virus, which indicates that the agent was very prevalent there.