Several types of organisms cause STIs. Those caused by bacteria or parasites can generally be cured. STIs caused by viruses generally cannot be cured, although they can be treated to relieve or eliminate symptoms. Most STIs are spread by sexual activity, and much of this spread can be prevented by the correct and consistent use of condoms. Some people, however, can get an STI in other ways. Details are provided in the table below. 

STI Types, Causes, Cures, and How They Are Spread

STI Type Sexual spread Nonsexual spread Curable?
Chancroid Bacterial Vaginal, anal, and oral sex None Yes
Chlamydia Bacterial Vaginal and anal sex rarely, from genitals to mouth From mother to child during delivery Yes
Gonorrhea Bacterial Vaginal and anal sex, or contact between mouth and genitals

From mother to child during delivery, or through breast milk

Contaminated blood transfusion

Yes
Hepatitis B Viral Vaginal and anal sex, or from penis to mouth

From mother to child during delivery, or through breast milk

Contaminated blood transfusion

No
Herpes Viral Genital or oral contact with an ulcer, including during vaginal and anal sex; also genital contact in area without ulcer From mother to child during pregnancy or delivery No
HIV Viral Vaginal and anal sex, or very rarely, oral sex

From mother to child during delivery, or through breast milk

Injection drug use with nonsterile needles

Contaminated blood transfusion

No
Human papillomavirus (HPV) Viral Vaginal, anal, and oral sex

From mother to child during delivery

No
Human T-lymphotropic virus  Viral

Vaginal and anal sex

From mother to child during delivery, or through breast milk

Contaminated blood transfusion

No
Syphilis Bacterial Genital or oral contact with an ulcer, including vaginal and anal sex

From mother to child during delivery, or through breast milk

Contaminated blood transfusion

Yes
Trichomoniasis Parasitic Vaginal, anal, and oral sex From mother to child during delivery Yes