Abstract
The first outbreak of influenza virus in Europe in 1995/1996 occurred in a school in the south of England. RT-PCR-restriction analysis was performed on the HA1 portion of influenza haemagglutinin gene amplified directly from clinical samples. These were taken at the onset of the outbreak and indicated co-circulation of two distinct genetic variants of influenza virus which were antigenically identical. Investigations of this nature demonstrate the genetic diversity of circulating variants of influenza and have the potential to provide information on molecular evolution of strains within closed populations.