Modelling the hepatitis C virus epidemic in Australia.

BACKGROUND: Hepatitis C virus (HCV) infection in Australia is predominantly transmitted through injecting drug use. A reduction in the heroin supply in Australia in late 2000 and early 2001 may have impacted the number of injecting drug users (IDUs) and consequently the number of new hepatitis C infections in Australia. This paper updates estimates of HCV incidence and prevalence between 1960 and 2005. METHODS: Simple mathematical models were used to estimate HCV incidence among IDUs, migrants to Australia from high HCV-prevalence countries, and other HCV exposure groups. Recent trends in numbers of IDUs were based on indicators of injecting drug use. A natural history of HCV model was applied to estimate the prevalence of HCV in the population. RESULTS: The modelled best estimate of past HCV incidence showed a consistent increasing rate of HCV infections to a peak of 14,000 new seroconversions in 1999, followed by a decline in 2001-2002 coincident with the decline in heroin availability. HCV incidence was estimated to be 9700 (lower and upper limits of 6600 and 13,200) in 2005. Of these, 88.7% were estimated to be through injecting drug use, 7.2% among migrants and 4.1% through other transmission routes. An estimated 264,000 (lower and upper limits of 206,000 and 318,000) people were HCV antibody positive in 2005. CONCLUSIONS: Mathematical models suggest that HCV incidence in Australia decreased from a peak of 14,000 new infections in 1999 to 9700 new infections in 2005, largely attributable to a reduction in injecting drug use. The numbers of people living with HCV in Australia is, however, estimated to continue to increase.

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.