OUTBREAKS OF INFLUENZA-A AMONG ELDERLY HOSPITAL INPATIENTS

Aims. To describe two outbreaks of influenza A that occurred in wards catering for assessment, treatment and rehabilitation of elderly patie nts at the Princess Margaret Hospital in Christchurch. Methods. Infect ed patients and staff were identified clinically, and influenza subseq uently confirmed or supported in some patients by viral antigen detect ion, culture of throat and nasopharyngeal swabs or serology. Results. Overall, the attack rate of clinical influenza in the two wards affect ed was 13 of 27 patients (48%) and 15 of 26 patients (58%) respectivel y. Of all those with influenza, 13 patients (46%) developed lower resp iratory tract infection and there were two deaths (7%) at least in par t attributed to influenza. Patients in single rooms were not protected from infection. The vaccination rate among all patients was 18%. Immu nised patients had a lower attack rate (21%) than those who had not re ceived influenza vaccine that season (40%). The attack rate amongst st aff in each ward was 69% and 36% respectively, and the overall staff v accination rate was 12%. Conclusion. These outbreaks illustrate the se vere consequences of influenza in an institutional setting.