LARGE SEQUENTIAL OUTBREAKS CAUSED BY INFLUENZA-A (H3N2) AND INFLUENZA-B VIRUSES IN AN INSTITUTION FOR THE MENTALLY-HANDICAPPED

During the mixed epidemic caused by influenza A (H3N2) and B in the 19 92-1993 season in Japan, large sequential outbreaks occurred in an ins titution for mentally handicapped people where none of the residents o r staff members had been immunized. During the influenza A outbreak (A /Beijing/32/92-like strain) in January, 37.0% of the residents (85/230 ) and 31.4% of the staff (75/239) had an influenza-like illness. Durin g the influenza B outbreak (B/Panama/45/90- and B/Beijing/184/93-like strain) in late February, 59.0% of the residents and 24.3% of the staf f had an influenzalike illness. As many as 25.2% of the residents had two episodes of influenza-like illness during the season, as opposed t o only 5.4% of the staff members. Mixed epidemics probably have a seve re impact on institutionalized high-risk people, adversely affecting t hem almost twice as much as influenza epidemics caused by a single vir us. (C) 1996 Wiley-Liss, Inc.