When someone has HIV one of the main places the virus can be found in their body is in their blood (in women this includes blood that is in her period).
The risk of HIV being transmitted through infected blood comes when it enters another person’s body or when it comes into contact with a mucous membrane (parts of the body with wet, absorbant skin such as the eye, vagina, head of the penis or inside the anus or the mouth). There is also a risk if infected blood comes into contact with a cut or broken skin, giving HIV a way through the skin and into someone’s bloodstream. If blood gets on skin that is not broken there is no risk.
The amount of HIV in blood can vary over time. Someone who has been infected with HIV in recent weeks or months has very high levels of the virus in their blood (and other body fluids such as semen and vaginal secretions). Once someone starts taking HIV drugs the level of HIV in their blood usually falls a lot.
The amount of HIV in blood can be measured by a ‘viral load test’. If HIV treatment is working well the result of the test can be ‘low’ or even ‘undetectable’. ‘Undetectable’ doesn’t mean that no HIV is in the blood, only that it is there in levels too low for the test to detect. Usually, the lower someone’s viral load, the less likely they are to pass HIV on, although even with ‘undetectable viral load’ some people have infected their partners.
As well as contact with blood during sex, sharing drug injecting equipment is another way infected blood can get into someone’s body. This can be avoided by using fresh needles and not sharing needles, syringes and other equipment. The same goes for peole who inject steroids.
Receiving a blood transfusion or other products made from blood is safe in the UK as since 1985 all blood products have been screened for infections like HIV. Giving blood has never been a risk.
HIV does not usually survive long outside of the body but contact with blood (especially on broken skin) should be avoided. To clean up blood that has been spilled on surfaces wear rubber gloves, mop up the liquid using bleach and warm water (one part bleach to ten 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.