A neurotropic virus was isolated from the blood of an African woman with fever. The serum taken at the time of illness contained no demonstrable neutralizing antibodies against the virus, whereas convalescent serum taken 3 months later neutralized strongly.
The virus has a particle size of approximately 21 to 31 mµ.
The virus is pathogenic for mice by intracerebral, intranasal, and intraperitoneal inoculations. It is slightly, if at all, pathogenic for mice by subcutaneous inoculation. It induces encephalitis and causes death when introduced intracerebrally in rhesus monkeys. It causes fever without obvious illness in African monkeys (Cercopithecus ethiops centralis) and induces the formation of neutralizing antibodies. It is not pathogenic for rabbits and guinea pigs, but induces the formation of antibodies.
Neutralization tests with this virus and appropriate immune sera may be carried out either by intracerebral or by intraperitoneal inoculation. Immunologically the agent is related to the virus of Japanese B encephalitis and perhaps also to the virus of louping ill.
The lesions induced by the virus are essentially limited to the central nervous system and are apparently different from the lesions induced by other known neurotropic viruses pathogenic for man.