by Associate Professor Gail Matthew | The Kirby Institute, University of New South Wales

For almost two decades it has been clear that rates of hepatitis C virus (HCV) transmission have been particularly high in HIV positive gay men, and not just in those engaging in injecting drug use. In many cities worldwide, especially within Europe, HCV acquisition among these men is mostly occurring through methods other than injecting drug use. In Australia around half of the HIV positive gay men acquiring HCV are infected in circumstances that do not involve injecting drug use. These transmissions are broadly categorised as ‘sexual’ exposures, meaning that transmission of the virus has occurred through sexual interaction(s) with an individual who is HCV positive. The exact risk and mechanisms are difficult to quantify but research studies have identified some situations in which sexual transmission may be more likely. These include having condomless anal intercourse, fisting, group sex, using sex toys and sex under the influence of other drugs taken by means other than injecting, including crystal. HCV is intermittently present in semen as well as in microscopic amounts of blood and it is likely that exposure to either of these may be responsible for transmission.

Although rates of sexually acquired HCV have been high in HIV positive gay men, the same has not traditionally been true in HIV negative gay men. Researchers have questioned whether this has been related to some difference in behaviours or some increased risk associated with being HIV positive. Although isolated cases of HIV negative gay men acquiring HCV through sex have been seen for some time, it appears that using condoms and ‘serosorting’ (i.e. only having sex with someone of the same HIV status) has prevented large numbers of transmissions within the broader gay community.

The widespread uptake of Pre-Exposure Prophylaxis (PrEP) to prevent HIV transmission has the potential to change this. Although extremely effective at preventing HIV, PrEP does not prevent transmission of other sexually transmitted infections, including HCV. Indeed, since the roll-out of PrEP there have been increases in the number of sexually acquired HCV infections in HIV negative men reported from European cities, including Amsterdam, London and Paris.

The good news is that treatment for HCV is now easy and highly effective. New drugs that can cure the virus are available that are taken as one pill a day for 8-12 weeks and result in almost everyone (>95%) being cured, whether you are HIV positive or not. These drugs have few or no side effects.

The Australian Government has made these drugs available on the Pharmaceutical Benefits Scheme for everyone who has HCV, whether it is their first, second or subsequent infection. By treating and curing as many people as possible within the community, the risk of new infections to others also drops. This is termed ‘treatment as prevention’. This is similar to ‘treatment as prevention’ for HIV in that it reduces transmission risk at the individual and population level. While a person living with HIV on effective treatment is not cured of HIV, when their viral load is suppressed to undetectable levels, they are not able to pass on HIV to their sexual partners. Likewise, a person cured of HCV cannot pass on the virus.

Since 2016 when these drugs first became available in Australia, treatment uptake has been one of the highest worldwide, especially in HIV positive people. We estimate that between 50-80% of HIV positive people living with active HCV have now been treated. This is having major health benefits, both for individuals and for society. To date reinfections among HIV positive people have been low, and importantly early data suggests that despite the widespread roll-out of PrEP in Australia, we are not observing the high rates of new HCV infections in HIV negative gay men seen elsewhere.

The note is one of cautious optimism. Risk still exists and not everyone has yet been treated. It is important to keep the conversations around HCV going with your partners and, if you are particularly concerned, there are ways to reduce your risk, including avoiding those situations in which HCV may be more readily transmitted and/or continuing to use condoms. However, testing regularly and keeping treatment rates high will be the key to ending HCV within the gay community of Australia.