Other sexually transmitted infections (STIs)

Other STIs in either the HIV negative or HIV positive partner can increase the risk of HIV transmission.

STIs include:

• Chlamydia.
• Genital warts (HPV – human pappiloma virus).
• Gonorrhoa.
• Syphilis.
• Herpes.
• LGV (lymphogranuloma venereum).
• Hepatitis A and B.
• Hepatitis C (for HIV positive gay men).
• Trichomoniasis.

STIs can reduce immune protection against other infections in HIV negative people. So HIV has a better chance of finding one of these cells. See Fig 10 (c) in the section Skin, mucous membranes and HIV transmission.

With herpes, for example, HIV target cells stay at much higher levels even weeks after a sore has cleared up. 

This is why HIV negative people with herpes, are at higher risk of catching HIV, even when they have no current sores.

Any sore is a way for HIV to enter the body.

An HIV positive person with an STI may be more infectious for HIV. This may also cause their undetectable viral load in blood to be at higher levels in genital fluid.

HIV positive people might also be at greater risk of catching STIs. For example, hepatitis C (HCV) is sexually transmitted for HIV positive gay men but rarely by heterosexual sex. 

The reasons for this are not clear.

HCV is usually transmitted by contact with infected blood.

If viral load is undetectable, there is no risk of HIV, even if there are other STIs.

PrEP also protects against HIV, even if there are other STI’s. PrEP does not protect against other STIs though.

Last updated: 1 June 2021.