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HIV transmission

how hiv is not passed on

Some body fluids, such as saliva, sweat and urine, do not have enough HIV in them to infect someone. HIV is not passed on by spitting, sneezing or coughing. If someone with HIV is on effective treatment with an undetectable viral load, they cannot pass on HIV.

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How is HIV transmitted?

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).

If you’re an injecting drug user, never share drug injecting equipment.

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

If someone with HIV is taking effective HIV medication and has an undetectable viral load, they cannot pass on HIV. It can take up to six months on treatment to become undetectable.

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 pregnancy if other contraception is not being used.

Some sexual activities have a greater risk of HIV infection than others.

When is a person with HIV infectious?

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

The risk is highest 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 reduce your viral load to undetectable levels and protect your health.

How is HIV not passed on?

Many activities pose no risk of getting or passing on HIV:

You cannot pass on HIV by:

  • kissing
  • hugging
  • shaking hands with somebody
  • any other normal social contact
  • sharing space with someone
  • sharing a toilet
  • sharing household items such as cups, plates, cutlery, or bed linen.

In the UK, there are safeguards in place to ensure that blood, organs and sperm donated for use in medical procedures are not HIV-infected.

A recent study called PARTNER found that people who are on effective HIV treatment and have an undetectable viral load cannot pass on HIV.

What is effective treatment?

The Partners PrEP study found that it can take up to six months on treatment for someone's viral load to become undetectable.

Effective treatment therefore means that someone has been taking it as prescribed for at least six months and has an undetectable viral load.

What about blood containing HIV?

In a medical setting, it's possible for HIV to be transmitted by someone accidentally cutting themselves with a blade or needle they have used to treat a person living with HIV.

This is called a needlestick injury and the risk of being infected in this way is very low - and can only happen if the person with HIV has a detectable viral load.

However, if someone thinks they have been exposed to HIV through a needlestick injury, Post-exposure Prophylaxis (PEP) may be an option.

How long can HIV survive outside the body?

Once outside the body, HIV usually can’t survive for very long. Coming into contact with blood or semen, from a person who has a detectable viral load, that has been outside the body doesn’t generally pose a risk for HIV transmission.

Similarly, the risk of passing on HIV to someone else if you have a detectable viral load and injure yourself is also very low. Wash away any blood with soap and hot water and cover the wound with a sticking plaster or dressing.

More on living with HIV:

This content is currently being reviewed and will be updated shortly.

Next: The immune system ››

‹‹ Previous: What is HIV?



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The Information Standard: Certified member

This article was last reviewed on 9/10/2017 by Anna Peters

Date due for the next review: 9/10/2020

Content Author: S. Corkery (NAM)

Current Owner: Kerri Virani

More information:

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