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 about 75% of cases, and these people are at risk of progressive liver fibrosis leading to cirrhosis, liver failure and hepatocellular carcinoma (HCC). About 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 (80%) of people with HCV infection have been diagnosed. [1-3] In Australia, before the direct-acting antiviral (DAA) era (from 2016), the prevalence of detectable HCV RNA (indicating viraemic or chronic HCV prevalence) was about 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 (e.g. 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 8,500–9,000 new infections in 2013, with stable incidence in recent years. [1,3]

Despite one of the highest HCV diagnosis rates in the world, treatment uptake in Australia was low (2,000–4,000 people/year, or 1%–2% of the infected population) before the DAA era. In contrast, since interferon (IFN)-free DAA regimens were listed on the Pharmaceutical Benefits Scheme (PBS) in March 2016, about 54,000 people have received HCV treatment (32,400 in 2016 and 21,500 in 2017; 24% of the population with chronic HCV infection) (Figure 1). [4]

Figure 1. Estimated number of people with chronic hepatitis C virus infection initiating treatment annually in Australia, 1997–2017

IFN = interferon. RBV = ribavirin. PegIFN = peginterferon. DAA = direct-acting antiviral. Source: Dore and Hajarizadeh. [4]

A key feature of the Australian HCV treatment landscape since the DAA program commenced has been the involvement of non-specialists in prescribing. Although the overall numbers of DAA treatment initiations per month have declined since March 2016, the contribution from general practitioners has remained relatively stable (Figure 2). [4]

Figure 2. Number of people initiating direct-acting antiviral therapy each month, March 2016 to June 2017, by prescriber type

Source: Dore and Hajarizadeh. [4]

In addition to efforts that increase the number of people treated overall, strategies that target populations with high HCV transmission risk will be required to facilitate HCV elimination by preventing new infections (“treatment as prevention”). A modelling study by Martin and colleagues showed that increasing treatment in PWID would have a dramatic effect on reducing HCV prevalence. [5] Using a baseline HCV prevalence of 50% among PWID in Melbourne, they predicted that increasing the annual treatment rate to 4% of PWID (8% of PWID with chronic HCV infection) would decrease HCV prevalence among PWID by 50% in 15 years. [5] An increase to 8% of PWID (16% of PWID with chronic HCV infection) would decrease prevalence in PWID by > 90% within a decade, essentially eliminating HCV infection from the Australian population of PWID. Clinical trials examining treatment as prevention in PWID and prison populations are ongoing in Australia.

Ongoing efforts will be required to sustain DAA treatment uptake, particularly among highly marginalised populations. Enhanced DAA access in drug and alcohol services, community clinics and prison clinics will be needed for HCV to be eliminated as a major public health issue in Australia.