Sexually transmitted disease

infection transmitted through human sexual behavior

A sexually transmitted disease (STD) is a disease which spreads by having sex. STDs can spread through oral sex or anal sex, or when two people's genitals touch. Today, STDs are usually called sexually transmitted infections (STIs). In the past, they were called venereal diseases (VD).

This painting showing Syphilis was attributed to Albrecht Dürer

STDs can be caused by viruses, bacteria, or parasites. Examples of the most common STDs are listed on this page.

Types of STDs

Numbers Sexually Transmitted Diseases in the US
Gonorrhoea world map

STDs caused by viruses


Human Immunodeficiency Virus (HIV)


HIV causes the immune system - the system in the body that is supposed to fight off infection - to not work as well as it should. This makes people with HIV more likely to get infections and some other diseases, like some cancers. HIV is the virus that causes AIDS.

Human papillomavirus (HPV)


There are about 40 different kinds of HPV that can be spread through sex and affect the anus and genitals.[1] Examples of diseases that HPV can cause include:

Hepatitis viruses


Hepatitis is an infection of the liver. There are three common types of hepatitis: hepatitis A, hepatitis B, and hepatitis C.

Hepatitis A causes a short-term liver infection. It can be spread by having sex, though this is not the most common way to get hepatitis A.[4]

Hepatitis B and hepatitis C cause much more serious, long-lasting liver problems. Both can cause very bad liver disease, like cirrhosis, and death. They are more likely than hepatitis A to be spread by having sex.[4]

Herpex simplex virus


The herpes simplex virus (HSV) causes genital herpes. Genital herpes can cause painful blisters on the genitals and anus. Herpes can also cause sores on the mouth.[5]

There is no cure for herpes.[5]

STDs caused by bacteria




Chlamydia is one of the common STDs in the world. In humans, it is the most common STD caused by bacteria.[6] In the United States alone, about 2.8 million more people get chlamydia infection every year.[7]

If chlamydia is not treated, it can cause serious problems, like diseases of the genitals and eyes. It can even cause blindness.[8] Chlamydia can also cause permanent damage to a woman's reproductive system if it is not treated.[4]



Gonorrhea can infect the genitals, rectum, mouth, throat, and eyes.[9] In bad cases, it can spread through the blood to infect the body's joints. In the worst cases, it can spread through the blood and infect the heart (causing endocarditis, an infection of the heart's valves) or the spinal cord (causing meningitis).[9]



Syphilis can cause many serious problems if it is not treated. It makes a person much more likely to get HIV, because it causes sores on the genitals that make it easier for HIV (and other STDs) to get spread.[10] After a few years, if people with syphilis do not get treated, they can have serious problems with the organs in their body. Eventually - without treatment - syphilis infects the brain and causes death.

STDs caused by parasites




Trichomoniasis is the most common STD in the world that is not caused by a virus.[11] It can cause inflammation swelling of the vagina (vaginitis, urethra (urethritis), or penis. It can also cause more serious problems. If it is not treated, it can cause permanent damage to a woman's reproductive system. It can also cause prostate cancer,[12] and makes a woman more likely to give birth to a premature baby.[13]



The only way for a person to be sure they will not get an STI is for that person not to have sex. This includes sex of any kind.[14]

There are some things that a person can do to make it less likely to get an STI:[14]

  • Practice safer sex: Use condoms.
  • Stay with one sexual partner who has tested negative for STDs
  • Do not have sex with anyone until you are both tested for STDs
  • Get the vaccines for HPV, hepatitis A, and hepatitis B

Other websites



  1. Division of STD Prevention (1999). Prevention of genital HPV infection and sequelae: report of an external consultants' meeting. Atlanta, GA: Centers for Disease Control and Prevention
  2. 2.0 2.1 Stanley, Margaret A; Winder, David M; Sterling, Jane C; Goon, Peter KC (2012). "HPV infection, anal intra-epithelial neoplasia (AIN) and anal cancer: current issues". BMC Cancer. 12 (1): 398. doi:10.1186/1471-2407-12-398. ISSN 1471-2407. PMC 3488563. PMID 22958276.
  3. "Summary of the WHO Position Paper on Vaccines against Human Papillomavirus (HPV)" (PDF). World Health Organization. 17 October 2014. Retrieved 23 January 2015.
  4. 4.0 4.1 4.2 "Sexually Transmitted Diseases (STDs)". National Institutes of Health – National Institute of Child Health and Human Development. May 28, 2013.
  5. 5.0 5.1 Balasubramaniam, R; Kuperstein, AS; Stoopler, ET (April 2014). "Update on oral herpes virus infections". Dental Clinics of North America. 58 (2): 265–80. doi:10.1016/j.cden.2013.12.001. PMID 24655522.
  6. Gerbase AC, Rowley JT, Mertens TE (1998). "Global epidemiology of sexually transmitted diseases". Lancet. 351 (Suppl 3): 2–4. doi:10.1016/s0140-6736(98)90001-0. PMID 9652711. S2CID 28976125.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. Chlamydia fact sheet from the Centers for Disease Control and Prevention
  8. Belland R, Ojcius D, Byrne G (2004). "Chlamydia". Nat Rev Microbiol. 2 (7): 530–1. doi:10.1038/nrmicro931. PMID 15248311. S2CID 11486211.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. 9.0 9.1 Marr, Lisa (2007) [1998]. Sexually Transmitted Diseases: A Physician Tells You What You Need to Know (Second ed.). Baltimore, Maryland: Johns Hopkins University. ISBN 978-0-8018-8658-4.
  10. Committee on Infectious Diseases (2006). Larry K. Pickering (ed.). Red book 2006 Report of the Committee on Infectious Diseases (27th ed.). Elk Grove Village, IL: American Academy of Pediatrics. pp. 631–44. ISBN 9781581102079.
  11. World Health Organization. Prevalence and Incidence of Selected Sexually Transmitted Infections, Chlamydia trachomatis, Neisseria gonorrhoeae, syphilis and Trichomonas vaginalis: Methods and Results Used by WHO to Generate 2005 Estimates. 2011. Available at:
  12. Caini, Saverio; Gandini, Sara; Dudas, Maria; Bremer, Viviane; Severi, Ettore; Gherasim, Alin (2014). "Sexually transmitted infections and prostate cancer risk: A systematic review and meta-analysis". Cancer Epidemiology. 38 (4): 329–338. doi:10.1016/j.canep.2014.06.002. ISSN 1877-7821. PMID 24986642.
  13. Secor W, Meites E, Starr M, Workowski K (2014). "Neglected parasitic infections in the United States: trichomoniasis". Am J Trop Med Hyg. 90 (5): 800–804. doi:10.4269/ajtmh.13-0723. PMC 4015567. PMID 24808247.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  14. 14.0 14.1 "Sexually Transmitted Diseases (STDs)". The Mayo Clinic. August 19, 2014. Retrieved January 2, 2015.