Production of Non-Infective Particles among Influenza Viruses: Do Changes in Virulence Accompany the von Magnus phenomenon?

Abstract

SummaryTwo new statistical methods—one parametric, the other non-parametric—are developed to compare the slopes of quantal infectivity curves.Ten influenza strains were examined with the aid of these tests, and the results show that virus yielded by the von Magnus phenomenon (i.e. containing ‘incomplete’ particles) and standard infective virus do not differ in the slope of their infectivity curves.It is concluded that the von Magnus phenomenon yields a mixture of infective and non-infective particles; on this evidence Fulton's suggestion of uniformly changed virulence is untenable.I am greatly indebted to Prof. P. A. P. Moran for helpful discussions of theory, and frequent corrections of statistical technique.