Hepatitis C spreading rapidly among HIV-positive MSM in Thailand and chemsex is a key risk factor

Crystal methamphetamine. Image by Find Rehab Centers. Creative Commons licence.

Hepatitis C is spreading rapidly among HIV-positive men who have sex with men (MSM) in Bangkok and is associated with use of crystal methamphetamine, research presented to the recent Conference on Retroviruses and Opportunistic Infections (CROI 2020) shows. Hepatitis C virus (HCV) infections were attributed to sexual transmission, a conclusion supported by a second study that identified a large HCV transmission cluster among MSM that involved a different strain of HCV to the one predominating among injecting drug users in Thailand.

Outbreaks of HCV infection have been reported among gay and other MSM in multiple cities around the world. Most of these infections involve men living with HIV. Most of the infections have been attributed to sexual transmission, with condomless receptive anal sex, fisting and group sex involving the use of stimulant drugs (chemsex) identified as key risk factors. Injecting drug use, especially in chemsex environments, also appears to have a role in transmissions.

Dr Donn Colby and colleagues from the Thai Red Cross AIDS Research Center used data collected for a study into the use of amphetamine-type stimulants to determine the prevalence and risk factors for HCV infection among MSM and transgender women in Bangkok.


transmission cluster

By comparing the genetic sequence of the virus in different individuals, scientists can identify viruses that are closely related. A transmission cluster is a group of people who have similar strains of the virus, which suggests (but does not prove) HIV transmission between those individuals.


The use of recreational drugs such as mephedrone, GHB/GBL and crystal meth before or during sex.


Receptive anal intercourse refers to the act of being penetrated during anal intercourse. The receptive partner is the ‘bottom’.


A sexually transmitted infection caused by the bacterium Treponema pallidum. Transmission can occur by direct contact with a syphilis sore during vaginal, anal, or oral sex. Sores may be found around the penis, vagina, or anus, or in the rectum, on the lips, or in the mouth, but syphilis is often asymptomatic. It can spread from an infected mother to her unborn baby.


An umbrella term for people whose gender identity and/or gender expression differs from the sex they were assigned at birth.

Recruitment took place at the Thai Red Cross Anonymous Clinic, and the final study population consisted of 470 individuals (94% MSM, 6% transgender women). At baseline, the participants were tested for HIV, HCV and sexually transmitted infections. They also completed a computer-assisted self-interview covering sexual and substance use risk behaviour.

Their median age was 28 years and 95% were employed or in education. Anal sex was reported by 94% of participants and group sex by a fifth. Half of those reporting group sex said this involved illicit drug use. Consistent condom use was reported by approximately 40%.

A total of 131 individuals (28%) said they had used amphetamine-like stimulants. This included 122 people who used methamphetamine.

A third of the sample was HIV positive and 18 people (3.6%) had antibodies to HCV. As regards STIs, 16% had a recent syphilis diagnosis, 8% infection with gonorrhoea and 16% chlamydia.

Closer analysis of those with HCV showed that just over a quarter (28%) had ever injected drugs, 24% reported using amphetamine-like drugs and 89% were HIV positive.

After taking into account potential confounders, the factors strongly associated with HCV infection were:

  • being HIV positive (OR = 16.15; 95% CI, 3.3-78.99, p = 0.001)
  • use of crystal methamphetamine (OR = 9.13; 95% CI, 2.63-31.75, p = 0.001)
  • taking oral amphetamines (OR = 9.48; 95% CI, 1.63-55.03, p = 0.012)
  • a recent STI (OR = 5.98; 95% CI, 1.54-23.2, p = 0.01)
  • being mainly receptive (bottom) for anal sex (OR = 4.3; 95% CI, 1.1-16.71, p = 0.036).

“Most cases of HCV appear to be transmitted by anal sex, potentiated by the presence of STIs and rough and prolonged sex in the context of illicit drug use,” conclude Colby and colleagues. “Harm reduction, and HCV treatment with direct-acting antivirals, are needed to address this newly emerging epidemic.”

A separate study, also conducted by investigators from the Thai Red Cross AIDS Research Center, identified two clusters of HCV transmissions among MSM in Bangkok.

Dr Win Min Han and colleagues examined the genetic sequence of HCV samples obtained from 48 MSM with hepatitis C and HIV co-infection (25 with recent HIV infection, 23 with long-standing HIV).

Their median age was 34 years, 83% had a history of syphilis and 36% reported the use of methamphetamine. Only two men reported injecting drugs and in both cases this was methamphetamine.

In 85% of cases, the HCV genotype was 1a, with the remaining 15% involving genotype 3a or 3b. “This epidemic is independent of past HCV transmission among people who inject drugs in Thailand, which was largely genotype 3,” note the investigators.

Phylogenetic analysis showed that 83% of HCV cases belonged to one of two transmission clusters – a large cluster involving 36 infections and a small cluster involving four cases. All clusters were genotype 1a. Individuals with recent HIV infection were more likely to be in a cluster than individuals with established HIV infection (92% vs 74%).

Full image credit: 'Crystal meth addiction'. Image by Find Rehab Centers. Available at www.flickr.com/photos/findrehabcenters/41626348764/ under a Creative Commons licence CC BY 2.0.


Colby DJ et al. The perfect ice storm: the mix of meth and HIV spreads hepatitis C in Thai MSM. Conference on Retroviruses and Opportunistic Infections, abstract 601, March 2020.

View the abstract on the conference website

View the poster on the conference website

Update: Following the conference presentation, this study was published in a peer-reviewed journal:

Wansom T et al. Group sex and methamphetamine use fuel an explosive epidemic of Hepatitis C among HIV-infected men who have sex with men in Bangkok, Thailand. JAIDS, published online ahead of print, April 2020.

doi: 10.1097/QAI.0000000000002356

Han WM et al. Large hepatitis C transmission cluster identified among HIV-positive MSM in Bangkok. Conference on Retroviruses and Opportunistic Infections, abstract 598, March 2020.

View the abstract on the conference website

View the poster on the conference website