Access to more effective hepatitis C treatment could halve new infections among men who have sex with men in the United Kingdom over the next decade, according to a modelling study presented at the International Liver Congress in Vienna, Austria, in April.
The model found that if 80% of men who have sex with men (MSM) are treated within a year of acquiring hepatitis C virus (HCV), and 20% of those with chronic infection are treated each year, incidence would be halved and the prevalence of HCV among MSM with HIV would fall below 3% by 2025.
Epidemics of hepatitis C have emerged among MSM living with HIV in Europe, North America and Australia over the past decade.
Studies of risk factors for HCV infection in MSM consistently show a strong association with unprotected anal intercourse, rectal bleeding, fisting and sex with multiple partners. (van de Laar 2010)
Sharing injecting equipment to inject methamphetamine and other stimulants during sex sessions has also been identified as a possible risk factor, but it is important not to overstate the role of injecting drug use in transmitting hepatitis C between gay men. Recent studies in the United Kingdom and United States show that the vast majority of men newly diagnosed with hepatitis C have no history of injecting drugs. (Ward 2014; Garg 2013)
Other forms of drug use appear to play an important role in HCV transmission. Some studies have found that sharing straws for snorting drugs is associated with acute infection. A large study of HIV-positive MSM in the United Kingdom found that HCV acquisition was associated with a history of using GHB and nitrites (poppers), both of which can be used during anal intercourse and sex parties.
Sharing sex toys and ulcerative sexually transmitted infections, usually syphilis, have also been associated with acute hepatitis C infection.
What almost all these factors have in common is their contribution to making blood-blood contact more likely during sexual activity. Many of these factors are likely to be synergistic: for example, use of GHB in a sex party may permit prolonged anal intercourse with multiple sex partners, leading to bleeding and rectal trauma.
Although the risk of hepatitis C infection can be minimised by condom use and safe injecting practices, epidemiologists have suggested that HCV incidence will only be checked among MSM and people who inject drugs by reducing HCV prevalence through curative treatment – treatment as prevention.
To estimate the potential effect of treatment on HCV incidence and prevalence in MSM in the United Kingdom, Natasha Martin of the University of California San Diego and colleagues in the United Kingdom developed a model of hepatitis C transmission among MSM using data from the UK Collaborative HIV Cohort (UK CHIC) and surveillance data on HCV infections.
The model assumed that 80% of men treated within a year of infection (acute cases) and 35% of men in chronic infection would be cured on interferon-based treatment, and that 90% of all men treated with interferon-free direct-acting antiviral regimens would be cured. The model assumed as a base scenario that 39% of newly infected men would be treated each year, and that 5% of chronically infected men would be treated each year.
Approximately 8.6% of MSM with diagnosed HIV infection were estimated to have hepatitis C in 2015. If current trends continue, and rates of treatment of newly infected men persist at a low level according to the base scenario, prevalence will increase to 10.8% by 2025, assuming that HIV diagnoses also continue to rise over the same period. However, even a low rate of treatment would have an effect on prevalence. Without any treatment at all, prevalence would have reached 11.6% in 2015 and would rise to 17% in 2025.
Scaling up treatment to treat 80% of newly infected cases and 20% of all chronic cases per year would reduce prevalence to under 3% by 2025, and would halve new infections, to less than 0.5 per 100 person years of follow-up.