STDs are caused through sexual contacts like vaginal intercourse, oral sex and anal sex. Other ways in which STD spreads:
Kissing or close body contact—for pubic lice infestation, scabies, and molluscum contagiosum
From mother to child before or during birth—for syphilis, herpes, chlamydial infection, gonorrhea, human immunodeficiency virus (HIV) infection, and human papillomavirus (HPV) infection
Breastfeeding—for HIV infection
Contaminated medical instruments—for HIV infection
Of late, it is being referred as sexually transmitted infection (STI); a person may be infected and might potentially infect others without showing any signs of disease.
sexually transmitted disease , also known as a sexually transmitted infection, or venereal disease, is an illness that has a significant probability of transmission between humans by means of human sexual behavior, including vaginal intercourse, oral sex, and anal sex.
STDs are sometimes referred to as sexually transmitted infections, since these conditions involve the transmission of an infectious organism between sex partners. STDs affect men and women of all ages and backgrounds, including children. Many states require that Child Protective Services be notified if children are diagnosed with an STD.
