HIV is transmitted only through direct transfer of blood, semen, vaginal fluids and breast milk. The most common ways in which this happens are:
- Unprotected sexual intercourse (either vaginal or anal)
- Unprotected oral sex (although the risk is less than from unprotected vaginal or anal sex)
- Needle-sharing when injecting drugs
- Unscreened and untreated transfusions of blood or blood products (blood products are screened for HIV in the UK)
- During childbirth from an infected woman to her baby.
Currently, the two groups most affected by HIV in the UK are gay men and heterosexual people who have lived in Africa. Although HIV infection is most common in these groups in the UK, anybody can be infected with HIV through unprotected sex or needle sharing.
Blood transfusions and the use of other blood products are safe in the UK, and mother to baby transmission can be prevented by proper treatment and care.
HIV is not transmitted by casual physical contact, coughing, sneezing and kissing, by sharing toilet and washing facilities, by using eating utensils or consuming food and beverages handled by someone who has HIV; it is not spread by mosquitoes or other insect bites.