Abstract
Search for influenza virus in the throats of apparently healthy persons in an institutional population revealed virus 32 days prior to an influenza epidemic in 1947, and during the epidemic, but not on other occasions. The virus strains, save one, isolated from influenza suspects and symptomless persons were antigenically similar and belong to the so-called A-prime type influenza. One strain isolated in 1947 appears to be antigenically unique in that it differs from all other strains isolated as well as from A and B type influenza viruses.