AN INFLUENZA VIRUS PNEUMONIA OF MICE THAT IS NONTRANSFERABLE BY SERIAL PASSAGE

It has been the usual experience that influenza virus pneumonia of mice is readily transmitted by serial passage; that is, suspensions of lungs from mice which die as the result of intranasal introduction of the virus produce death, or at least extensive pulmonary lesions, when introduced into normal mice by the intranasal route. However, during the adaptation of the Cam strain of influenza A prime virus to nice, we observed that, although the infected allantoic fluid killed the mice on the third or fourth day with complete pulmonary consolidation, suspensions of lungs obtained from those animals did not produce pulmonary lesions when introduced into the lungs of normal mice. Anderson and Burnet (1947) previously had reported similar results with the Cam strain of virus, but they did not show whether or not the virus particles present in the allantoic fluid were responsible for the mouse virulence. The present investigation was undertaken in order to obtain data on that point.