An Epidemic of Influenza a due to an Atypical Strain. The Relationship of This Strain to Other Influenza Viruses

Abstract

An epidemic due to atypical strains of influenza A appeared in the population regardless of prophylactic vaccination. High titers to the viruses in the vaccine were found in the acute phase sera indicating the potency of the vaccines. The relationship of these new strains to known viruses of influenza is discussed. Differences in strains occurring during the same epidemic have been found. No relationship between this epidemic and previously noted increases in antibodies to the porcine virus could be determined. The data suggest that the new strains were introduced into a highly susceptible population. Precautions against interference in the isolation of influenzal viruses must be taken.