A sexually transmitted disease (STD) or venereal disease (VD), is an illness that has a significant probability of transmission between humans or animals by means of sexual contact, including vaginal intercourse, oral sex, and anal sex. Increasingly, the term sexually transmitted infection (STI) is used, as it has a broader range of meaning; a person may be infected, and may potentially infect others, without showing signs of disease. Some STIs can also be transmitted via the needles used in IV drug use, as well as through childbirth or breastfeeding. Sexually transmitted infections have been well known for hundreds of years.