How do people become infected with HIV?

How do people become infected with HIV?

In order for a person to become infected, a sufficient amount of HIV must enter their bloodstream. This sufficient amount is the amount of HIV found in some, but not all, of the body fluids of someone with HIV or AIDS.

In a person with HIV or AIDS, the body fluids which contain enough HIV to infect someone else are:

• blood
• sperm and seminal fluid
• vaginal fluids, including menstrual fluids
• breast milk

Other body fluids like saliva, sweat or urine do not contain enough virus to infect another person.

If HIV is present in body fluids, it still cannot enter another person's body easily. There are a limited number of routes:

• directly into the bloodstream; for example, via a puncture caused by injection equipment
• via an organ transplant or blood transfusion
• through the 'interior' skin (mucus membrane) of the rectum, vagina, cervix and urethra. The urethra is in front of the vagina in women and is the 'tube' in the penis in men
• very rarely, through the eyes, mouth or throat

HIV cannot pass through intact external skin. It cannot pass through the air like cold germs.

See the Trust's booklet Preventing HIV Infection for information on preventing HIV transmission.