One-step growth curves of five strains of influenza A, one strain of swine influenza, and three strains of influenza B virus have been analyzed.

The influenza A and swine influenza strains showed constant periods of 5 to 6 hours before newly formed virus was liberated from the infected cells, whereas 8 to 10 hours elapsed in the case of the influenza B strains.

The yield of virus in the allantoic fluids, i.e. the number of ID50 released for every ID50 of seed virus adsorbed, was consistently higher in the case of the influenza A and swine influenza strains than in that of the influenza B viruses.

Interruption of the cycle by injection of inactivated virus subsequent to infection can be achieved by any of the strains of the homologous type. However, cross-tests between influenza A and swine influenza virus led only to partial inhibition of virus growth.

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