What is the difference between sexually transmitted infection (STI) and sexually transmitted disease (STD)?

These terms are often confused, but they are not inter-changeable. Sexually transmitted infection is the broadest term. All STDs are STIs, but not all STIs are STDs.

Sexually Transmitted Infection: Invasion of and multiplication in bodily tissue by a microorganism (eg, bacterium, virus, protozoan) that is usually (more than half the time) passed from one person to another during intimate bodily contact meant to give or derive sexual gratification.

Sexually Transmitted Disease: Pathology (ie, damage) with or without symptoms secondary to an infection that is usually (more than half the time) passed from one person to another during intimate bodily contact meant to give or derive sexual gratification.

Reviewed: May 2016

Which viral STIs are curable and which are incurable?

Herpes and HIV:
These are the only two viral STIs which are always chronic. Even though people with herpes or HIV cannot currently be cured, their symptoms can be treated. At this time, there are no available vaccines to prevent Herpes or HIV. However, there are medications available to help prevent the HIV virus from causing infection in the sexual partners of HIV positive people.1

About 9 out of 10 sexually active people will become infected with the human papillomavirus at some point in their lives. Up to 90% of HPV infections are cleared by the body’s immune system within 12-24 months of detection.2 Some types of HPV are low-risk for cancer, but can cause genital warts. Those who are infected with high-risk (cancer-causing) HPV types and do not clear their infection quickly are at risk for persistent infection. There is no cure for persistent HPV. Persistent HPV infection is a risk factor for development of cervical cancer and oral cancer in men. All women should have routine pap smears by age 21.

There are currently two available vaccines to help prevent HPV infections. The most recent vaccine, Gardasil 9, protects against 9 different strains of the HPV virus, including most of the cancer-causing types and most of the wart-causing types. Both girls and boys are encouraged to be immunized with the vaccines. The vaccine can be given as early as age 9.3

Hepatitis B:

In the U.S., babies usually get there first does of hepatitis B vaccine at birth and then two more doses of the vaccine by the time they are 18 months old. Adults who were born before 1991 may not have received the vaccine. They should be vaccinated if they are at risk for Hepatitis B exposure.4

Most adults who are infected with hepatitis B virus (HBV) recover from their infections; the rest develop chronic infections.  Each year 2,000-4,000 people in the U.S. die from cirrhosis or liver cancer caused by hepatitis B.4

Hepatitis C:
There is no vaccine to prevent Hepatitis C. About 75%-85% of people infected with Hepatitis C will develop chronic hepatitis C and 60-70% will develop chronic liver disease.5 Hepatitis C is spread through the blood, but can be sexually transmitted.

Hepatitis C can be cured with medication, especially if the treatment begins within 6 months of getting the disease. Since 2013, more medications have been approved for use in chronic hepatitis C, resulting in increasing cure rates.6


1. Centers for Disease Control and Prevention, “Sexually Transmitted Diseases Treatment Guidelines, 2015,” MMWR Reomm Rep 2015; 64(no. RR)
2. Grimes, Jill (Editor) Sexually Transmitted Disease: An Encyclopedia of Diseases, Prevention, Treatment, and Issues, 2014GREENWOOD, Santa Barbara, Ca.(Vol. 1)
3. Centers for Disease Control and Prevention, “Human Papillomavirus (HPV) Vaccine Safety,” http://www.cdc.gov/vaccinesafety/vaccines/hpv-vaccine.html
4. Medline Plus,”Hepatitis B Vaccine,                                                                                                                    http ://www.nlm.nih.gov/medlineplus/druginf/meds/a607014.html                                                          5. Center for Disease Control and Prevention, “Hepatitis C FAQs for Health Professionals,”
http://www.cdc.gov/hepatitis/HCV/HCVfaq.htm  Accessed May 2016                                                      6. AASLD/IDSA, “Recommendations for testing, managing, and treating Hepatitis C,”
http://www.hcvguidelines.org Accessed May 2016


Updated: Nov. 2016.

Should parents discuss sex with their teens?

Absolutely. Multiple studies demonstrate that parent-child communication has an important protective effect on adolescent sexual behavior.1-3 Parents need to be actively involved with their teens and take time to clearly communicate their own values and expectations.

– Teens who feel close to their parents are much less likely to engage in risky behavior.4
– Teens whose parents express disapproval of nonmarital sex and contraceptive use are less likely than their peers to have sex.5
– Teens who talk to a parent about sex tend to wait to have sex, have fewer sexual partners, and are more likely to name apparent than a peer as a good source of information about sex.6


1. Karofsky PS, Zeng I., Kosorok MR. Relationship between adolescent-parental communication and initiation of first intercourse by adolescents. J Adolesc Health. 2000;28(1):41-45.
2. Resnick M, Bearman D, Blum R, et al. Protecting adolescents from harm. Findings from the national longitudinal study on adolescent health. JAMA. 1997;278(10):823-832.
3. Dilorio C, Kelley M, Hockenberry-Eaton M. Communications about sexual issues: mothers, fathers, and friends. J Adolesc Health. 1999;24(3):181-189.
4. Jaccard J, Dittus P, Gordon V. Parent-teen communication about premarital sex: factors associated with the extent of communication. J Adolesc Res. 2000;15(2):187-208.
5. Lederman RP, ChanW. Roberts-Gray C. Sexual risk attitudes and intentions of youth aged 12-14 years; survey comparisons of parent-teen prevention and control groups. Behav Med. Winter 2004;29(4):155-163.
6. Whitaker d, miller K. Parent-adolescent discussions about sex and condoms: impact on peer influences of sexual risk behavior. J Adolesc Res. 2000;15(2):251-273.

Reviewed: June 2012

What is secondary virginity?

“Secondary virginity” is a return to abstinence following sexual debut. A commitment to secondary virginity is often made with the goal of remaining abstinent until committing to a life-long monogamous relationship, such as marriage. Increasing numbers of teens and young adults are making this decision to reduce their considerable risk for sexually transmitted infections and nonmarital pregnancies. Parents, peers, family physicians, youth directors, teachers, and health educators all play important roles in encouraging sexually active youth to turn to abstinence.

Reviewed: June 2012.

What is abstinence?

Abstinence is refraining from all sexual activity.

Sexual activity refers to actions intended to result in sexual arousal or gratification.
– Sex includes penile-vaginal, anal and oral sex.
– Other actions intended to result arousal or gratification, including, but not limited to, masturbation, mutual masturbation, fondling, the use of sex toys, and the viewing of pornography.

Reviewed: May 2016

What can be done about the epidemics of STIs and nonmarital pregnancy facing our country?

People who postpone sexual activity until marriage to an uninfected partner are completely protected from STIs and nonmarital pregnancy. If this behavior choice (ie, abstinence) were to become normative again, it is likely that these epidemics would be reversed.

There is evidence that many teens are getting this message. According to Youth Risk Behavior Surveillance data, over half of teens in high school have not had sexual intercourse.1 From 1991 through 2011 the number of teens who have not had sexual intercourse increased from 46% to 52.6%.2 Additionally, the number of teens with four or more lifetime partners decreased significantly from 1991 to 2011.2 Most adolescents will postpone sexual activity (become or remain abstinent) with proper instruction and encouragement, especially from parents.

1. Centers for Disease Control and Prevention. Youth Risk Behavior Surveillance – United States, 2011. Surveillance Summaries, June 8, 2012. MMWR 2008;61(No. SS-4). Available at: http://www.cdc.gov/mmwr/pdf/ss/ss6104.pdf. Accessed: June 29, 2012.

2. 2. Centers for Disease Control and Prevention. Trends in the Prevalence of Sexual Behaviors and HIV testing: National YRBS 1991-2011. Available at: http://www.cdc.gov/healthyyouth/yrbs/pdf/us_sexual_trend_yrbs.pdf. Accessed: June 29,2012.


Reviewed: June 29, 2012.

What is the impact of nonmarital teenage pregnancy?

Since 1990, the teen pregnancy rate in the U.S. has dropped by half. However, In 2010 (most current statistics) there were approximately 614,000 teen pregnancies in the U.S. Based on this statistic, a teenage girl has a 1 in 4 chance of getting pregnant at least once before the age of 20.1

A pregnancy can either lead to a live birth, a miscarriage, or an abortion. In 2010, 60% of teen pregnancies resulted in a live birth, 15% in miscarriage, and 26% resulted in abortion.1 The majority of teen mothers were unmarried when their child was born (88% in 2010).2

Teenage mothers are more likely than older mothers to experience:
• Serious health and emotional problems3-6
• Poverty7
• Less education7
• Single parenthood2

Fathers of children born to teen mothers are more likely than other fathers to experience:8-10
• Decreased earnings
• Less education
• Depression
• Compared to older fathers, teen fathers are
— less likely to have plans for a future job
— more likely to have anxiety
— more likely to be homeless or in unstable household

Children born to teen mothers are more likely than other children to experience:11-17
• Health problems
• Abuse and neglect
• Poverty
• Less education
• Incarceration


  1. Kost K, Henshaw S and Carlin L, U.S. Teenage Pregnancies, Births and Abortions: National and State Trends and Trends by Race and Ethnicity, 2010. http://www.guttmacher.org/pubs/USTPtrends.pdf . Accessed June 26, 2012.
  2. National Campaign to Prevent Teen and Unplanned Pregnancy, “Why it Matters: Teen childbearing, Single Parenthood and Father Involvement,” http://thenationalcampaign.org/resource/why-it-matters-teen-childbearing-single-parenthood-and-father-involvement  Accessed May 2016
  3. Miles MS, Holditch-Davis D, Schwartz TA, Scher M. Depressive symptoms in mothers of prematurely born infants. J Dev Behav Pediatr. 2007;28(1):36-44.
  4. Kalil A, Kunz J. Teenage childbearing, marital status, and depressive symptoms in later life. Child Dev. 2002;73(6):1748-1760.
  5. Brooks DW, “Teenagers and High Risk Pregnancy,” http://pregnancy.lovetoknow.com/wiki/Teenagers_and_High_Risk_Pregnancy Accessed May 2014
  6. Gillmore MR, Gilchrist L, Lee J, Oxford ML. Women who gave birth as unmarried adolescents: trends in substance use from adolescence to adulthood. J Adolesc Health. 2006;39(2):237-243.
  7. National Campaign to Prevent Teen and Unplanned Pregnancy, “Why it Matters: Teen Childbearing, Education, And Economic Wellbeing,” http://thenationalcampaign.org/resource/why-it-matters-teen-childbearing-education-and-economic-wellbeing Accessed May 2016
  8. Hofferth SL, Reid L, Mott FL. The effects of early childbearing on schooling over time. Fam Plann Perspect. 2001;33(6):259-67.
  9. Quinlivan JA, Condon J. Anxiety and depression in fathers in teenage pregnancy. Aust N Z J Psychiatry. 2005;39(10):915-920.
  10. Heath DT, Mckenry PC, Leigh GK. The consequences of adolescent parenthood on men’s depression, parental satisfaction, and fertility in adulthood. J Soc Serv Res. 1995;20(3-4):127-48.
  11. da Silva AA, Simoes VM, Barbieri MA, et al. Young maternal age and preterm birth. Paediatr Perinat Epidemiol. 2003;17(4):332-329.
  12. Chen XK, Wen SW, Fleming N, Demissie K, Rhoads GG, Walker M. Teenage pregnancy and adverse birth outcomes: a large population based retrospective cohort study. Int J Epidemiol. 2007;36(2):368-373.
  13. Cunnington AJ. What’s so bad about teenage pregnancy? J Fam Plann Reprod Health Care. 2001;27(1):36-41.
  14. Harden KP, Lynch SK, Turkheimer E, et al. A behavior genetic investigation of adolescent motherhood and offspring mental health problems. J Abnorm Psychol. 2007;116(4):667-683.
  15. Zhou Y, Hallisey EJ, Freymann GR. Identifying perinatal risk factors for infant maltreatment: an ecological approach. Int J Health Geogr. 2006;5:53.
  16. Gueorguieva RV, Carter RL, Ariet M, Roth J, Mahan CS, Resnick MB. Effect of teenage pregnancy on educational disabilities in kindergarten. Am J Epidemiol. 2001;154(3):212-220.
  17. National Campaign to Prevent Teen and Unplanned Pregnancies, “Why it Matters: Teen Childbearing and Infant Health”http://thenationalcampaign.org/resource/why-it-matters

Updated: May 2016

What makes adolescent females so susceptible to STIs?

In all females the cervix is covered with two cell types – epithelial (skin-like) cells and columnar (like the cells lining the intestine) cells. In mature females, the outer part of the cervix (ie, the part the doctor sees when he or she looks at the cervix to obtain cells for a PAP smear) is covered with multiple layers of hardy (squamous) epithelial cells, and the upper part inside the cervical canal is lined with fragile columnar cells. Where the two cell types meet is referred to as the squamocolumnar (SC) junction.

The location of this junction varies considerably between adolescents/young females and mature females.
Adolescents/young females have a normal condition referred to as ectopy. With ectopy, the junction between the two cell types is somewhere on the outer cervix (where a physician could see it on pelvic exam) rather than inside the cervical canal. The more ectopy there is, the larger the diameter of fragile columnar cells on the outer exposed surface of the cervix. In addition to being highly susceptible to STIs, the exposed columnar and SC junction cells are more easily transformed into precancerous cells or into cancer if infected with human papillomavirus.

Reviewed : May 2016

What is meant by “consistent” condom use?

Consistent condom use means using a condom 100% of the time during every sex act. Few individuals actually manage to use condoms consistently and correctly for any length of time. Typical condom use is inconsistent. Studies have shown that even in couples in which one partner is known to be infected with HIV, consistent use was attained by only 45% of participants.1

How do teens fare? A study conducted over a period of 6 months found that “always” condom use was reported by adolescent females only 13% of the time.2 In another study, just 50% of females reported consistent condom use.3 Generally, adolescent males report slightly more condom usage than females.4

Unfortunately, inconsistent condom use provides little to no risk reduction for most STIs. According to an NIH panel on condom effectiveness, even if 100% consistent condom use could be attained, it would not totally eliminate the risk of acquiring any STI, including HIV.5


1. Buchacz K, van der Straten A, Saul J, et al. Sociodemographic, behavioral, and clinical correlates of inconsistent condom use in HIV-discordent heterosexual couples. J Acquir Immune Defic Syndr 2001;28(3):289-297.
2. Bunnell RE, Dahlberg L, Rolfs R, et al. High prevalence and incidence of sexually transmitted infections in urban adolescent females despite moderate risk behaviors. J Infect Dis 1999;180(5):1624-1631.
3. Crosby RA, DiClemente RJ, Wingood GM, et al. Value of consistent condom use: a study of sexually transmitted infection prevention among African American adolescent females. Am J Public Health 2003;93(6)901-902.
4. Centers for Disease Control and Prevention. Trends in HIV- and STD- related risk behaviors among high school students- United States, 1991-2007. MMWR 2008;57:817-822. Available at: http://cdc.gov/mmwr/PDF/wk/mm5730.pdf. Accessed 2012 June 29.
5. National Institutes of Health. Workshop Summary: Scientific evidence on condom effectiveness for sexually transmitted infection prevention. Bethesda, MD: National Institutes of Health, US Dept of Health and Human Services; 2001.

Reviewed: June 29, 2012

I heard that there are 6 steps to correct condom use. What are they?

According to the Centers for Disease Control and Prevention (CDC), condoms must be used correctly to be effective in reducing the spread of STIs. The following steps are required to correctly use a condom:1

* Use a new condom with each sex act (e.g., oral, vaginal, and anal).
* Carefully handle the condom to avoid damaging it with fingernails, teeth, or other sharp objects.
* Put the condom on after the penis is erect and before any genital, oral, or anal contact with the partner.
* Use only water-based lubricants (e.g., K-Y Jelly™, Astroglide™, AquaLube™, and glycerin) with latex condoms. Oil-based lubricants (e.g., petroleum jelly, shortening, mineral oil, massage oils, body lotions, and cooking oil) can weaken latex.
* Ensure adequate lubrication during vaginal and anal sex, which might require the use of exogenous water-based lubricants.
* To prevent the condom from slipping off, hold the condom firmly against the base of the penis during withdrawal, and withdraw while the penis is still erect.
Almost no studies actually measure correct condom use. In a study of college males, more than a third reported major errors in condom use over a three month period, despite having received instructions on correct use.2

1. Centers for Disease Control and Prevention. Sexually Transmitted Diseases Treatment Guidelines, 2010. MMWR 2010;59(No. RR-12):1-116. Available at: http://www.cdc.gov/std/treatment/2010/STD-Treatment-2010-RR5912.pdf.  Accessed: 2012 June 29.
2. Crosby RA, Sanders SA, Yarber WL, et al. Condom use errors and problems among college men. Sex Transm Dis 2002;29(9):552-557.

Reviewed: June 29, 2012.

How many people in the US are infected with an STI? Are many of those infected people adolescents?

It is estimated that in 2013 there were:1
– 20 million new cases of STIs
– 110 million total cases of STIs- a combination of new infections and long-term infections

About half of the new cases occurred in 15- to 24- year olds, even though they make up only 25% of the sexually active population. Data from the 2014 STD surveillance, shows both the numbers and rates of reported cases of Chlamydia and Gonorrhea occurred among 15 – 24 year olds.2

1. Satterwhite CL, et al. Sexually transmitted infections among U.S. women and men: Prevalence and incidence estimates, 2008. Sex Transm Dis 2013; 40(3): pp. 187-193.

2. Centers for Disease Control and Prevention, “Reported STDs in the United States: 2014 national Data for Chlamydia, Gonorrhea, and Syphilis,” http://www.cdc.gov/std/stats14/std-trends-508.pdf Accessed May 2016


Updated: May 2016

How many STIs are there and what are their names?

The number of STIs (sexually transmitted infections) will vary depending on what is counted as an STI and whether sexually transmissible infections are counted. The Medical Institute uses a list of STIs that is adapted from chapter headings in a standard STI textbook1. This list, which appears below in alphabetical order, has 27 different infections.

1. bacterial vaginosis
2. chancroid
3. chlamydia
4. donovanosis
5. gonorrhea
6. lymphogranuloma venereum
7. mycoplasma, genital
8. syphilis
9. treponematosis, endemic

10. lice, pubic
11. scabies
12. candidiasis, vulvovaginal

13. amebiasis
14. cryptosporidium
15. giardiasis
16. trichomoniasis

17. cytomegalovirus
18. Epstein Barr virus
19. hepatitis A
20. hepatitis B
21. hepatitis C
22. hepaptitis D
23. herpes simplex virus (HSV-1 and HSV-2)
24. human immunodeficiency virus (HIV)
25. human papillomavirus (HPV)
26. human T-cell lymphotropic virus (HTLV-1)
27. molluscum contagiosum

1. Holmes KK, Sparling PF, Stamm WE, et al. Sexually Transmitted Diseases, 4th Ed. New York, NY: McGraw Hill Medical; 2008.

Reviewed: June 29, 2012.

How serious of a problem are sexually transmitted infections (STIs) in the United States?

For many reasons it is difficult to determine the exact prevalence (number of currently infected people) or incidence (number of new cases per year) of sexually transmitted infections.

However, the STI incidence rate was estimated at 18.9 million per year for the year 20001– a 6 million increase over a 1996 estimate.2 Below are incidence and prevalence rate estimates for STIs:2-7


STIs in the US2-7
Incidence and Prevalence Estimates
STI Incidence* Prevalence**
HPV2 6 million 20 million
Trichmoniasis3 7.4 million unknown
Chalmydia4 1.2 million 2 million
Genital Herpes 1 million 45 million
Gonorrhea4 301,000 unknown
Hepatitis B5 38,000 Up to 1 million
Syphilis4 14,000 Unknown
HIV 50,000 1.2 million


* Number of new infections occurring in the population in one year

** Number of infections found in the population including those from previous years


1. Weinstock H, Weinstock H, Berman S, Cates W Jr. Sexually transmitted diseases among American youth: Incidence and prevalence estimates, 2000. Perspect Sex Reprod Health. 2004;36(1):6-10.

2. Centers for Disease Control and Prevention. Tracking the Hidden Epidemics: Trends In STDs In the United States, 2000. Atlanta GA: Department of Health and Human Services, Centers for Disease Control and Prevention; 2000. Available from: http://www.cdc.gov/std/Trends2000/default.htm. Accessed: June 29, 2012.

3. CDC. Genital HPV Infection. Atlanta: U.S. Department of Health and Human Services; 2009. Available from: http://www.cdc.gov/std/HPV/STDFact-HPV.htm. Accessed June 29, 2012.

4. CDC. Trichomoniasis. Atlanta: U.S. Department of Health and Human Services; 2007. Available from: http://www.cdc.gov/std/trichomonas/STDFact-Trichomoniasis.htm. Accessed June 29, 2012.

5. CDC, Trends in Sexually Transmitted Diseases in the United States, 2009: National Data for Gonorrhea, Chlamydia and Syphilis. Atlanta: U.S. Department of Health and Human Services; 2010. Available from: http://www.cdc.gov/std/stats09/trends.htm. Accessed June 29, 2012.

6. CDC. Disease Burden from Viral Hepatitis A, B, and C in the United States. Atlanta: U.S. Department of Health and Human Services; 2010. Available from: http://www.cdc.gov/hepatitis/Statistics/index.htm  Accessed June 29, 2012.

7. Centers for Disease Control and Prevention. HIV/AIDS in the United States: At a Glance Fact Sheet. Atlanta, GA: Department of Health and Human Services, Centers for Disease Control and Prevention; 2012 March. Available at: http://www.cdc.gov/hiv/resources/factsheets/PDF/HIV_at_a_glance.pdf. Accessed 2012 June 29.

Reviewed: June 29, 2012.

What is the difference between “reported” and “estimated” STI cases?

“Reported” STI cases are those for which the results of a medical test have been reported at the local, state, or federal level. While STI reporting requirements and mechanisms have improved, they do have limitations. Even the best national STI reporting system falls far short of determining the actual number of STI cases. Here are some reasons:
– many STIs cause no symptoms at all or result in “delayed” symptoms
– for a variety of reasons, even when they have symptoms of an STI, some people still don’t seek medical care (e.g., they may not know where to go; they may not have the financial resources to pay for treatment; they may deny that they have symptoms)
– Doctors often treat patients for STIs without performing a laboratory test that would help them make a specific diagnosis
– Doctors and laboratories may fail to report patients with laboratory-confirmed STIs

Public Health officials are highly aware of the limitations of the reporting system, and consider all of these factors when they “estimate” the number of STI cases.1

For example, although just over 350 thousand cases of gonorrhea were reported in 2014, the CDC estimates  that approximately 820 thousand cases occur each year in the U.S.2

1. Centers for Disease Control and Prevention, “Reported STDs in the United States: 2014 National Data for Chlamydia, Gonorrhea, and Syphillis,” CDC Fact Sheet  http://www.cdc.gov/std/stats14/std-trends-508.pdf accessed May 2016.

2. Centers for Disease Control and Prevention, “Gonorrena – CDC Fact Sheet (Detailed Version)” http://www.cdc.gov/std/gonorrhea/STDFact-gonorrhea-detailed.htm   Accessed May 2016.


Updated: May 2016