HIV, HCV and sex

Sexual transmission of HIV

The majority of new HIV infections globally each year are because of sexual transmission.

The ways that HIV is transmitted are well understood. HIV is present in blood, semen, genital fluids and breast milk.

Different types of sex carry different risks; for example, body rubbing and mutual masturbation are zero risk, oral sex is usually low risk, and anal or vaginal sex without a condom is usually high risk. Condoms are very effective at reducing HIV transmission.

Viral load in the HIV positive partner is related to each of these risks. Risks are dramatically lower when HIV viral load is undetectable.

Some other sexually transmitted infections (STIs), including herpes, gonorrhoea and syphilis, increase the risk of transmitting HIV. This is because they increase the amount of HIV in genital fluids and make the HIV positive partner more infectious.

STIs also increase the risk of catching HIV in several ways. An open sore is an easy route of infection but also immune responses to an STI make it easier for HIV to take hold.

All this information is important when talking about HCV.

Sexual transmission of HCV

The risk for sexually transmitted HCV is more complicated. 

HCV is still primarily a blood borne infection so sex that includes blood-to-blood has the highest risk.

Although HCV has been found in semen, and vaginal fluid it is unclear whether these fluids are infectious, because HCV is generally at very low levels. Even though HCV levels can be high in semen and do not always match HCV levels in blood, contact with sexual fluids is unlikely to be a major route of HCV infection.

The risk of HCV sexual transmission is low from vaginal sex, in monogamous, HIV negative heterosexual couples in which one partner has HCV. However, much higher rates of sexual transmission have been reported in HIV positive gay men, for reasons that are not clear.

The importance of two aspects of this increased risk still have to be explained.

  • The role of HIV, perhaps because of reduced immune protection or higher HCV viral load in HIV positive people with coinfection.
  • The type of sex some HIV positive men have – behavioural differences – and how this may be different to HIV negative gay men as a group. This may be because of a higher risk of blood-to-blood contact.

Because cases of HCV have been reported where sexual transmission is the most likely route – both from heterosexual and gay sex – UK guidelines currently recommend that people with coinfection use condoms for penetrative sex.

Heterosexual transmission of HCV

The risk of heterosexual sexual transmission of HCV in people who are HIV negative is so low that condoms are not routinely recommended. 

  • The risk is generally reported as less than 1% per year.
  • In these studies, couples did not use condoms, but also did not have anal sex or have sex during menstruation. The reason for this protection is likely to be through reduced exposure to blood-to-blood contact.
  • Although contact with menstrual blood has not been reported as a common factor in heterosexual partners, this has not been well studied.
  • In HIV positive people, the risk for sexually acquiring HCV is higher than that reported for monogamous, HIV negative heterosexual couples.
  • One study reported that sexual exposure is a risk factor for HIV positive women who do not inject drugs but have male partners with HCV. There is very little information about whether these women were using HIV treatment and whether their HIV viral load was undetectable, or about the HIV status of their partners.

Sexual transmission of HCV in gay men

HCV sexual transmission among HIV positive gay men has been reported in cities in the UK, Europe, Asia, Australia and the US. 

Limited research has associated sexual HCV transmission with sevral risks which may or may not be a directly related:

  • Being HIV positive.
  • Recreational drug use.
  • Group sex and sex parties.
  • Sharing sex toys.
  • Rougher sex (longer fucking or fisting).
  • Barebacking (insertive or receptive anal sex without condoms),
  • Other STIs (especially syphilis).
  • Meeting partners online.
  • Number of partners.
  • Rectal bleeding from surgical procedures and/or rough sex.

As many of these experiences overlap, it is difficult to identify the exact cause.

Some HIV positive gay men have caught HCV sexually without these risks, for example, without fisting, using recreational drugs or taking part in group sex.

HIV as a factor

HIV seems to be an important factor in catching HCV because sexual transmission in HIV negative gay men has been much less reported.

  • HIV seems to be an important factor in catching HCV because sexual transmission in HIV negative gay men is not as common.
  • Even with ART, a high CD4 count and low viral load, immune responses to HCV are lower than in HIV negative people.
  • This is shown by a lower rate of spontaneous HCV clearance and a longer time to develop HCV antibodies.
  • HIV positive people may also be more infectious, as HCV viral load is higher (by about 10 times) compared to HIV negative men.

The role of blood vs genital fluids?

When HCV is detected in genital fluids, levels are generally low – levels in blood and much higher. Blood is therefore likely to be much more infectious compared to semen during the first six months of infection (called acute infection).

  • In the few studies measuring HCV in semen one found higher levels in HIV positive compared to HIV negative men and one found no difference.
  • This second study found that acute HCV was linked to higher HCV levels in semen which might be the important difference given most HCV infections in gay men have been recent.
  • Although higher HCV viral load increases the chance of HCV in semen, some men have very high HCV in blood and undetectable levels in semen.
  • HCV is also found in rectal fluid.

Recreational drug and HCV infection

Although HCV is transmitted during sex seems among HIV positive gay men, recreational drug use increases this risk in several ways. 

This includes non-injection use of party drugs such as crystal meth, cocaine and ecstasy.

  • Recreational drugs can lower your immune responses so you may be more vulnerable to HCV infection.
  • Recreational drugs can dilate blood vessels make the lining of the anus more vulnerable to tears and bleeding.
  • Recreational drugs can act as muscle relaxants allow longer and more energetic sex.
  • Recreational drugs also reduce inhibitions and are commonly used during group sex.
  • Injecting recreational drugs, including mephedrone and crystal meth, has a high risk of HCV transmission if needles or other equipment are shared.

type of sex, group sex and sex parties

Any activity with a risk for contact with traces of blood (rather than semen, which is the route for most STIs) is likely to be significant for HCV transmission. 

  • Semen may be infectious if a partner is in acute HCV infection. People with chronic HCV (for more than six months) are likely to have higher levels of HCV in their blood than their semen.
  • At least one study has reported high levels of HCV in rectal fluid.
  • Some recreational drugs, sharing toys and lube, rougher anal sex, fisting, and group sex are linked to higher HCV risk.
  • Because HCV is so much more infectious than HIV, it is more easily transmitted during group sex. Rougher, longer sex, increases the chance of bleeding.
  • In group sex, someone who fists more that one partner can transfer HCV without having become infected themselves.
  • Recreational drugs increase risk in at least three ways: tissue is more vulnerable to damage, sexual inhibition can change behaviour, and sex may be rougher and go on for longer.
  • One study also reported that sex after recent surgery or treatment for anal warts was a high risk for catching HCV. This would be an easy route for the virus to enter the bloodstream.
  • Other STIs, especially syphilis, are linked to acute HCV infection. Routine health checks are important to protect you health and that of your partners.


The three recreational drugs commonly referred to as ChemSex have often been reported as being linked to sexual HCV transmission.

These three drugs are crystal meth, mephedrone and GHB/GBL: “meth, meph and G”.

Compared to other recreational or party drugs, ChemSex drugs keep people high for much longer, often for several days.

These drugs are used in an almost exclusively sexual context. ChemSex has therefore been linked to high rates of STI transmission, including HIV and HCV.

PrEP and HCV

PrEP is a way for to HIV negative people to use oral HIV meds to dramatically reduce the risk of becoming HIV positive – even when not using condoms.

Although PrEP is highly effective against HIV – more than 99.9% when taken as prescribed – it doesn’t protect against other STIs, including HCV.

Several PrEP studies, including UK-based, reported HCV transmission in gay men.Where HCV is a concern, condoms are likely to provide some level of protection and are therefore still recommended in UK guidelines.

PDF leaflet: Safer HCV sex for gay men

Safer HCV sex for gay men

Although similar safer sex information is often given for HCV as for HIV, the risk from HCV is more likely to come from contact with blood than semen.

  • UK guidelines recommend condoms.
  • Use a new condom with each partner.
  • Use latex gloves for fisting and a new glove with each partner.
  • Condoms and gloves need to be thrown away more carefully than when just considering HIV. Unlike with HIV, the outside of the condom (or glove) may be more infectious than the inside.
  • Any cause of anal bleeding, including recent surgery, increases the chance of HCV sexual transmission.
  • Blood is likely to be more infectious compared to semen or rectal fluid during chronic HCV. Semen might be more infectious during acute HCV.
  • Don’t share lube from a pot. Traces of blood will not be visible and HCV remains infectious out of the body for at least 16 hours and perhaps for days or weeks.
  • Recreational drugs can increase the risk of bleeding because blood flow is increased. They can enable sex to be rougher or to go on for longer and they can reduce someone’s awareness of their risk.
  • Use condoms on sex toys. If you share sex toys, use a new condom every time.
  • Be aware that in group sex HCV can be transmitted by someone who does not have HCV themselves. For example, from onward contact with traces of blood from a previous partner.
  • Other STIs are linked to acute HCV infection. Routine health checks are easy. Early diagnosis and treatment are important ways to look after your health and your partners health.
Although many people use drugs recreationally, higher use of crystal meth, mephedrone and GHB/GBL is directly related to recent increases in demand for drug and alcohol services.  These are the three key ChemSex drugs.
Antidote is a drug and alcohol service for lesbian, gay, transgender and bisexual people, based in London with a national phoneline: 020 7833 1674 (10am-6pm, Monday to Friday).

Last updated: 17 August 2017.