The epidemiology of HCV in Australia
Hepatitis C virus (HCV) infection is a major public health challenge for Australia. Acute infection progresses to chronic disease in up to 75% of cases, and these people are at risk of progressive liver fibrosis leading to cirrhosis, liver failure and hepatocellular carcinoma (HCC). Around 20%–30% of people with chronic HCV infection will develop cirrhosis, generally after 20–30 years of infection.
In Australia, the diagnosis of HCV infection has required mandatory notification since the early 1990s. HCV notifications by jurisdictions are forwarded to the National Notifiable Diseases Surveillance System, with recording of information including age, sex and year of diagnosis. Total HCV notifications and estimates of HCV incidence and prevalence in at-risk populations, particularly among people who inject drugs (PWID), indicate that a high proportion (75%–82%) of people with HCV infection have been diagnosed.1-3 In Australia, the prevalence of detectable HCV RNA (indicating viraemic or chronic HCV prevalence) is approximately 0.9% (range, 0.7%–1.0%) or 227,000 people (range 167,620–249,710).2
The incidence of new HCV infections in Australia has declined since 2000, related to both a reduction in the prevalence of injecting drug use and improved harm reduction measures (eg, needle and syringe programs and opioid substitution treatment uptake) among PWID. The proportion of new HCV cases in young adults (aged 20–39 years) provides the best estimate of incident cases. Modelling suggests that the incidence of HCV infection peaked at 14 000 new infections in 1999 and had declined to 8500–9000 new infections in 2013.1,3 Despite this decline in HCV incidence, prevalence is increasing and the overall burden of liver disease continues to increase, due to the ageing of the population with chronic HCV infection and suboptimal HCV treatment uptake and outcomes. The increasing liver disease burden is reflected in escalating rates of end-stage liver disease, including HCC and liver failure, as well as HCV-related liver transplantation.
Despite one of the highest HCV diagnosis rates in the world, treatment uptake in Australia was low (2000–4000 people/year, or 1%–2% of the infected population) through 2015 (Figure 1). In contrast, during the period from March to December 2016, following Pharmaceutical Benefits Scheme (PBS) listing of interferon-free direct-acting antiviral (DAA) regimens, an estimated 32 400 people (14% of the population with chronic HCV infection) commenced HCV treatment.4
Modelling of the Australian HCV epidemic examined strategies to reduce projected HCV-related morbidity and mortality with the planned availability of well tolerated and highly effective DAA agents.5 In 2013, most people living with HCV were estimated to have mild liver fibrosis, and only 6% (13 850) to have compensated cirrhosis. However, without an increase in treatment uptake or efficacy, the number of people with compensated cirrhosis will almost triple to 38 000 by 2030, with concomitant increases in the number of people with HCC (n = 2040) and liver-related death (n = 1740). The modelling showed that increasing sustained virological response (SVR) rates AND increasing the number of people treated each year will be necessary to effect a substantial reduction in HCV prevalence and HCV-related mortality (Figure 2).5
In addition to efforts that increase the number of people treated overall, strategies that target populations with high HCV transmission risk could accelerate HCV elimination by preventing new infections (“treatment as prevention”). A modelling study by Martin and colleagues recently showed that increasing treatment in PWID would have a dramatic effect on reducing HCV prevalence.6 Using a baseline HCV prevalence of 50% among PWID in Melbourne, they predicted that increasing the annual treatment rate to 40 per 1000 PWID would decrease HCV prevalence among PWID by 50% in 15 years.6 An increase to 80 per 1000 PWID would decrease prevalence in PWID by > 90%, essentially eliminating HCV infection from the Australian population of PWID. Clinical trials examining treatment as prevention in PWID have recently commenced in Australia.
Armed with a detailed understanding of the epidemiology of HCV infection and the unrestricted access to highly effective and well tolerated oral DAAs through the PBS, it is very likely that the onward transmission of the virus can be halted and that HCV can be eliminated as a major public health issue in Australia.