Antiviral prophylaxis in the management of an influenza outbreak in an aged care facility.

Influenza in persons aged > or = 65 years is associated with an increased risk of severe complications. Residents in aged care facilities have a higher proportion of chronic illnesses and within closed settings there is an increased risk of transmission. In July 2002, a 50 bed aged care facility reported an influenza-like illness (ILI) among residents and staff despite over 90 per cent influenza vaccine coverage among residents. A total of 17 of 49 residents and 9 of 43 staff met the case definition for ILI with onset on or after 26 June 2002. Seven people required hospitalisation and two died. Nasopharyngeal swabs were collected from symptomatic residents and staff, and influenza A was detected in six residents and two staff. Five unimmunised residents and 33 unimmunised staff were offered influenza vaccine and all residents and staff were offered oseltamivir prophylaxis of 75mg daily for 10 days. Subsequently, of 41 residents tested, seven demonstrated a fourfold or greater rise in antibody titres specific to H3N2 yet reported no symptoms. All seven had been immunised at least eight weeks previously, and had taken oseltamivir prophylaxis. This outbreak was characterised by a high attack rate of ILI in a well-immunised community. The ability to access rapid diagnostic testing enabled the prompt initiation of antiviral prophylaxis, which may have a role in controlling influenza in this setting.