Abstract
During the present summer a recurrence of epidemic encephalitis has taken place in St. Louis and St. Louis County. Clinically the disease appears similar to that seen in the same area in the summer of 1933. On September 21, 1937, we reported before the St. Louis Medical Society 1 the successful recovery of a strain of the virus of the present outbreak, the original inoculation being made on August 28, 1937. This had been successfully carried through 4 series of white mice. At that time the first virus neutralization test was in progress but the final report was not available. This virus has now been carried through 8 transplantations in mice. Its virulence for mice is practically identical with that of the virus of 1933. Two strains of the 1933 virus were recovered and studied by two of us in the laboratories of Firmin Desloge Hospital, 2 subsequent to the isolation of the virus by Webster and Fite. 3
We are now able to report the completion of the 3 virus neutralization tests demonstrating the degree of protection afforded by the serum of 3 patients who had acute attacks of encephalitis in the summer of 1933 against the virus of the 1937 outbreak.
Virus neutralization tests were carried out on the sera of these same patients during 1935 and 1936 against the 1933 virus. These tests are included for comparison with the present tests.
The results are summarized in Table I.
The significance of these results is to indicate the identity of the virus causing the 1937 summer outbreak of encephalitis with that which caused the epidemic of 1933. It also points to the existence of an endemic focus of this infection in the St.
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