Infections transmitted from one person to another during sexual intercourse and possibly other sexual activities. STIs include HIV, syphilis, gonorrhoea, chlamydia and human papillomavirus (HPV). It is important to note that some STIs can be acquired through non-sexual means, particularly through contact with blood from an infected person, e.g. from mother to child during pregnancy or birth, through the use of contaminated needles or through blood transfusions. The term ‘sexually transmitted infection’ is now used more often than ‘sexually transmitted disease’ because it includes HIV; after becoming infected with HIV, years often pass before a person develops HIV disease (AIDS).