How is HIV transmitted?
If someone with HIV has a detectable viral load, they can pass on HIV through the following body fluids:
- blood
- semen (including pre-cum)
- vaginal fluid
- anal mucus
- breast milk.
People can get HIV through:
- vaginal/frontal and anal sex without a condom
- sharing drug injecting equipment
- sharing sex toys
- mother-to-child transmission during pregnancy
- coming into contact with contaminated blood.
Most activities pose no risk of getting or passing on HIV.
HIV cannot be passed on by:
- kissing
- hugging
- shaking hands
- sharing space with someone
- sharing a toilet
- sharing household items such as cups, plates, cutlery, or bed linen
- any other general social contact.
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 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 cut yourself is also very low. Wash away any blood with soap and hot water and cover the wound with a sticking plaster or dressing.
How do you get HIV from semen or vaginal fluid?
Body fluids including semen and vaginal secretions can contain HIV. If a person has HIV and a detectable viral load, HIV can passed on to someone if their semen or vaginal secretions get into the body of a sexual partner during vaginal or anal sex.
You can get HIV if you have vaginal or anal sex with someone who has HIV and a detectable viral load without using protection (like condoms or HIV prevention pill PrEP).
If the semen of someone who has HIV and a detectable viral load gets into the body of their sexual partner during sex, then HIV can get into the other person’s bloodstream and infect them.
Pre-cum also contains HIV – this is why there remains a risk of infection even if, during sex, the insertive partner pulls out before ejaculation.
If the vaginal secretions of someone who has HIV and a detectable viral load come into contact with a penis during sex, then HIV could be transmitted – the virus in secretions can enter through the delicate skin of the penis or foreskin.
Do condoms stop HIV being passed on?
Yes. Using a condom correctly prevents contact with semen or vaginal secretions (and blood), stopping HIV from being passed on. The virus cannot pass through the latex of the condom.
Condoms should only be used with a water-based lubricant as oil-based lube weakens them.
People with HIV who are on effective treatment and have an undetectable viral load cannot pass on HIV through any of their body fluids.
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.
Mother-to-child transmission
This is now extremely rare in the UK because the following medical interventions reduce the risk of mother-to-baby transmission to below 1%:
- The mother taking treatment (if she is not already doing so).
- The mother may be offered a Caesarean if the mother's viral load is detectable.
- The baby is given a course of HIV treatment for the first few weeks.
- The mother not breastfeeding.
How could you get HIV from contact with blood?
The risk of HIV transmission through blood comes when the person has a detectable viral load and their blood enters another person’s body or comes into contact with a mucous membrane. These are parts of the body with wet, absorbent skin such as the:
- eyes
- vagina
- head of the penis
- inside of the anus
- mouth.
There’s also a risk if blood from a person who has a detectable viral load comes into contact with a cut or broken skin, giving HIV a way through the skin and into someone’s bloodstream. If blood gets onto skin that isn’t broken, there is no risk.
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. The risk of being infected in this way is very low. However, if someone thinks they have been exposed to HIV through a needlestick injury, post-exposure prophylaxis (PEP) may be an option.
How to be safe when coming into contact with infected blood
A condom will act as a barrier against any contact with blood during sex.
As well as sex, sharing equipment for injecting drugs (including steroids) is a way blood can get into someone’s body. This can be avoided by using fresh needles and not sharing needles, syringes and other equipment.
If a woman has HIV, her menstrual blood also carries a risk of transmission if she has a detectable viral load.
If you’re HIV negative and taking pre-exposure prophylaxis (PrEP) you’ll be protected against getting HIV if you come into contact with infectious blood.
What should I do if I need to clean up blood?
HIV does not usually survive long outside of the body, but contact with blood (especially on broken skin) should be avoided.
Hepatitis C can survive in dried blood at room temperature for several weeks, and hepatitis B can survive in dried blood for around a week outside the body.
To clean up blood that has been spilled, wear rubber gloves and mop up the liquid using bleach and warm water (one part bleach to 10 parts water). Use warm, soapy water to clean away blood spilled on someone’s body.
Put the waste, used gloves and bloodied clothes in a plastic bag, seal and throw away.
Can you get HIV from a blood transfusion?
Receiving a blood transfusion or other products made from blood is safe in the UK as all blood products have been screened for infections such as HIV since 1985.
In countries that don’t have strict checks on the safety of their blood supply, receiving contaminated blood can pass the virus on. This can also happen in countries that don’t screen other blood products, organs or sperm.
Giving blood has never been a risk.
