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How is HIV passed on?

how hiv is passed on

HIV is found in the body fluids of a person living with HIV. There may be enough HIV to be infectious in semen, genital fluids*, blood and breast milk. However if someone with HIV is on treatment with an undetectable viral load they cannot pass on HIV.

*Definition of genital fluids: Vaginal and cervical secretions, semen (cum), pre-ejaculate (pre-cum) and rectal secretions

How is the HIV virus transmitted?

To pass on the virus, infectious body fluids need to get into someone else’s bloodstream.

If someone with HIV is taking HIV medication and has an undetectable viral load they cannot pass on HIV.

If someone with HIV is infectious they can pass on HIV through the following body fluids:

  • blood
  • semen (including pre-cum)
  • vaginal fluid
  • anal mucus
  • breast milk.

This can be prevented by using a condom during sex, or by the HIV negative person taking Pre-exposure prophylaxis (PrEP).

People who inject drugs can avoid HIV being passed on by not sharing drug injecting equipment.

During pregnancy your doctor will advise you how to protect your baby.

How is HIV passed on during sex?

During sex body fluids from someone with HIV can get inside a person who is HIV negative.

If the person with HIV has a detectable viral load the virus can enter the HIV negative person’s bloodstream. This can happen during vaginal and anal sex (and sometimes oral sex too, though this is much less common).

It can also happen when an object (eg, a sex toy) that has infectious body fluids on it is put inside an HIV negative person.

It’s also important to remember that if you have sex without a condom other sexually transmitted infections (STIs) can be passed on.

Sex without a condom can also result in an unplanned pregnancy if other contraception is not being used.

When is a person with HIV infectious?

Someone with HIV is infectious if they have a detectable viral load.

This is often during the first few months after infection when they have very high levels of the virus in their body fluids and may not yet have been diagnosed.

Early diagnosis means you can start treatment to protect your health and reduce your viral load to undetectable levels.

What is protected sex?

Protected sex is where you use a male or female condom during sex if one of you has HIV and a detectable viral load.

Condoms should be used with water-based lubricant as oil-based lube weakens them.

HIV treatment is also a form of protection.

How HIV treatment stops HIV being passed on:

  1. A person with HIV who is taking treatment and has an undetectable viral load cannot pass on HIV.
  2. PrEP, when taken correctly, significantly reduces the chances of becoming HIV positive. PrEP is a course of HIV drugs taken by an HIV negative person to lower the chance of infection.
  3. Post-exposure prophylaxis (PEP), when started in time, can stop HIV infection after sex without a condom (or other exposure) with someone who is infectious - but it does not work every time. PEP is a month-long course of HIV medication taken by an HIV negative person after possible exposure to reduce the chance of getting HIV.
  4. If a woman is pregnant, HIV medication is part of the way mother to baby transmission can be prevented.

Other risk factors

HIV isn’t actually as infectious as many other STIs. It isn’t automatically passed on every time a positive person with a detectable viral load and a negative person have unprotected sex, for example.

Other factors that can affect the risk of HIV being passed on:

More about HIV:

Next: How is HIV not passed on? ››

‹‹ Previous: The stages of HIV infection



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This article was last reviewed on 23/1/2015 by Anna Peters

Date due for the next review: 23/11/2018

Content Author: Kerri Virani

Current Owner: Kerri Virani

More information:

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