SUSCEPTIBILITIES TO RIMANTADINE OF INFLUENZA A H1N1 AND A/H3N2 VIRUSES ISOLATED DURING THE EPIDEMICS OF 1988 TO 1989 AND 1989 TO 1990/

Clinical isolates of influenza A viruses identified during outbreaks i n two winters were tested for their rimantadine susceptibilities by an enzyme-linked immunosorbent assay modified from that described previo usly by Belshe et al. (R. B. Belshe, B. Burk, F. Newman, R. L. Cerruti , and 1. S. Sim, J. Virol. 62:1508-1512, 1988). The infectivity titer and the 50% inhibitory concentration of rimantadine were calculated fo r each virus. Of 105 influenza virus A isolates tested, 28 influenza A /H1N1 isolates from the 1988 and 1989 outbreak and 77 influenza A/H3N2 isolates from the outbreak in following year, were susceptible to the antiviral action of rimantadine.