Viral Load and HIV Transmission

Viral load is the term used to describe the levels of HIV in the body at any one time. It is determined through a blood test.

A higher viral load is associated with a higher risk of HIV transmission.  With successful HIV treatment, the viral load can become very low or ‘undetectable’ in the blood, and this significantly reduces the risk of HIV transmission.

The amount of virus in the blood is usually connected with the viral load in other bodily fluids – semen, vaginal fluid and rectal fluid (the fluids commonly associated with the sexual transmission of HIV).  This means that when the viral load in the blood decreases, it generally also decreases in other fluids.  However, the viral load in each of the bodily fluids can sometimes be different.

For many people on long term HIV treatment, with an undetectable viral load, the risk of transmitting the virus to a partner(s) is negligible.

The risk may be higher if other STIs are present.  For example, if an HIV positive person is not on treatment, some STIs can increase the viral load making it easier for HIV to be transmitted.  HIV negative partners are also at increased risk of HIV infection if they have an STI.

A lot of people with HIV see the reduction of infectiousness as a very important benefit of HIV treatment, decreasing anxiety about transmission.  People are now taking their viral load into consideration when thinking about safer sex.

If you want to stop using condoms, it is important to discuss this carefully with your partner(s) and ensure they are also comfortable with the decision.  This information may be new to a lot of people who do not have HIV; it may take time for someone to understand and trust what you are saying.  It is also important to remember that while using this approach will protect your partner(s) from HIV, it does not protect them or you from other STIs.

The following are some guidelines for people who may be thinking about using this approach to reduce the risk of HIV transmission:

  • Check to make sure the blood viral load is undetectable before starting this approach, and get regular viral load tests to ensure it remains undetectable.  As a guideline, it is suggested that people wait until the viral load has been undetectable for at least six months before making any decisions about whether to stop using condoms.
  • The viral load can increase if doses of HIV treatment are missed.  Take pills exactly as prescribed.  Adherence to treatment is critical to keep the viral load undetectable.
  • Get tested regularly for STIs.  If either partner has an STI, start treatment immediately and consider using condoms during this time.
  • If you have not already done so, get vaccinations for hepatitis A and B.
  • Use other HIV prevention strategies as much as possible, particularly condoms and lube.  This will help reduce the overall risk of HIV transmission.
  • If this approach is used without disclosing your HIV status, it is important to remember that in some countries having sex without condoms without disclosing that you are HIV positive is a criminal offence, regardless of the likelihood of HIV transmission.