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
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
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
The model doesn’t look at cost-effectiveness, and the
researchers say that this is their next step. They also want to look at the
impact of HCV transmission from people with undiagnosed HIV infection to
HIV-negative people, and to look at whether HCV transmission is having any
effect on HIV transmission, and vice versa.