The virus of lymphocytic choriomeningitis produces an intense systemic infection in Syrian hamsters with few if any clinical and pathological signs of disease. Specific soluble antigen is demonstrable in the spleen of infected animals until about the 14th day when antisoluble substance antibodies make their appearance. Circulating virus disappears after the 4th week and neutralizing antibodies are present in serum in detectable amounts shortly thereafter; both types of antibody persist for at least several months.
The viruses of St. Louis encephalitis and lymphocytic choriomeningitis can be concurrently passed in series in the brains of hamsters. The resultant disease is indistinguishable from that caused by the virus of St. Louis encephalitis alone.