Aims: To describe two outbreaks of influenza A that occurred in wards catering for assessment, treatment and rehabilitation of elderly patients at the Princess Margaret Hospital in Christchurch.
Methods: Infected patients and staff were identified clinically, and influenza subsequently confirmed or supported in some patients by viral antigen detection, culture of throat and nasopharyngeal swabs or serology.
Results: Overall, the attack rate of clinical influenza in the two wards affected was 13 of 27 patients (48%) and 15 of 26 patients (58%) respectively. Of all those with influenza, 13 patients (46%) developed lower respiratory tract infection and there were two deaths (7%) at least in part attributed to influenza. Patients in single rooms were not protected from infection. The vaccination rate among all patients was 18%. Immunised patients had a lower attack rate (21%) than those who had not received influenza vaccine that season (40%). The attack rate amongst staff in each ward was 69% and 36% respectively, and the overall staff vaccination rate was 12%.
Conclusion: These outbreaks illustrate the severe consequences of influenza in an institutional setting.