Science Series

2007

Sexually Transmitted Infections

Understanding These Infections and Planning for Future Research and Prevention

MARCH 2006 NIH Scientific Workshop Focuses the Discussion

What are STIs?

Why are STIs important?

Why are STIs a 

women’s issue?

How can women 

prevent STIs?

What are barriers to 

healthy behaviors?

What is NIH doing 

about STIs?

NIH resources for

 health consumers

What Are STIs?

Sexually transmitted infections (STIs), commonly 

called sexually transmitted diseases (STDs), are often 

undetectable. They can be transmitted by those affected 

to unsuspecting partners during intimate physical contact, 

including sex, through oral, anal, or vaginal routes. More 

than 20 different kinds of STIs have been identified. These 

can be grouped by origin: 

• STIs caused by bacteria can be treated and often cured 

with antibiotics. Among these are chlamydia, gonorrhea, 

trichomoniasis, and syphilis. 

• STIs caused by viruses can be controlled, but not cured.

Viral STIs include HIV/AIDS, genital herpes, genital 

warts, human papilloma virus (HPV), hepatitis B virus, 

and cytomegalovirus.

Why Are STIs Important?

STIs present a major public health problem, both nationally 

and globally. Not only do they have devastating effects 

on the health of women and their children, but having an 

STI greatly increases the risk for developing HIV and AIDs. 

The Centers for Disease Control and Prevention (CDC) 

estimates that 19 million new infections are reported each 

year in the U.S. with direct medical costs estimated at 

$14.1 billion. The numbers reflect only those cases that 

have been diagnosed and reported. Many cases of human 

papilloma virus and genital herpes, highly prevalent viruses,

are not reported at all presenting an even greater risk for 

transmission. The U.S. must also be concerned with the 

global impact and spread of STIs since the rates in Africa 

are slightly more than double and those in Asia triple our 

reported figures. Young people, ages 15 to 24, account for 

almost half of these new STIs. 

Why Are STIs a Women’s Issue?

Women are more susceptible to and affected 

by STIs and their consequences. Young adolescent girls are most vulnerable to contracting 

STIs because of the normal hormonal changes 

that occur in puberty, the limited exposure of their 

immune systems, and their increase in cervical 

abnormalities. Despite these biologic risks, adolescents are not usually attuned to these diseases and 

are often more concerned about pregnancy than they 

are of contracting an STI. If symptoms develop, they 

are often minor or nonspecific, particularly in the early 

stages of an STI. Symptoms may also be attributed 

to other diseases that are not associated with sexual 

contact (e.g., yeast and urinary tract infections). As a 

result, STIs in women sometimes are not diagnosed until 

after serious problems have developed. For example, 

women with gonorrhea or chlamydia can develop pelvic 

inflammatory disease (PID), which can lead to ectopic 

pregnancy and infertility. STIs in pregnant women may 

result in perinatal infection with adverse effects to the 

fetus or newborn, including death. STIs are often the 

source of lifelong chronic pelvic pain conditions.

Most importantly, having an STI puts women in this sexually 

active group at a 6-7 fold risk for contracting HIV and a 5 fold 

risk for transmitting the virus to an unsuspecting partner. In 

the U.S., HIV/AIDS is the sixth leading cause of death among 

all women aged 25 to 34 and the fourth leading cause of 

death among all women aged 35 to 44.

How Can Women Prevent STIs?

The only way for women to ensure that they will not contract 

an STI is to avoid all types of intimate sexual contact. However, 

if women are sexually active, there are several ways they can 
reduce their risk of infection. These include using a condom 

every time they have vaginal, oral, or anal intercourse, 

knowing their partner and his or her STI status and health, 

and having regular medical checkups, especially if they have 

more than one sexual partner.

Both sexes in the adolescent group most likely to develop 

new STIs have not yet achieved the full cognitive maturity 

necessary for exercising good judgment in the context of a 

wide array of high risk situations, making it unlikely that they 

practice these safe behaviors. 

What Are Barriers To Healthy 

Behaviors?

In addition to the biologic and psychological challenges 

presented, gender plays an important role in the transmission 

and prevention of STIs. Gender is different from one’s sexual 

biology. Gender is defined by socially constructed roles that 

are assigned to men and women in any given society and that 

may vary, but in some respects, are remarkably similar among 

different cultures. Many social factors impact gender roles 

in the U.S. and can influence how or if women take steps to 

prevent and/or seek treatment for STIs. Such social factors 

include: 

• Economic forces—Women generally earn less than 

men. This can affect women’s access to health care and 

cause some women to make sexual decisions based on 

economic reasons rather than health reasons.

• Educational differences—Differences in educational 

attainment can also create imbalances of power and 

economic status that affect women’s sexual health 

decisions.

• Partner violence—Many women are victims of assault 

and control. They may be unwilling or unable to control 

their sexual safety. They also may experience the social 

isolation and depression that go along with partner 

violence, both of which are risk factors for STIs.

• Fear of abandonment—Many women fear being left by 

men, which can affect decisions about their sexual health 

and safety.

Health professionals and educators must attend to the overriding importance of these factors and deliver culturally 

relevant, targeted messages to effectively control STIs. 

What Is NIH Doing About STIs?

The information presented here was compiled from a 2006 

NIH Office of Research on Women’s Health seminar to 

increase awareness and scientific understanding of how STIs 

affect health. Distinguished presenters who shared their 

expertise were Victoria A. Cargill, M.D., MSCE; Roberta Black, 

Ph.D.; Craig R. Cohen, M.D., M.P.H.; and Kathy Woodward, 

M.D. The NIH also sponsors numerous efforts to combat STIs 

which include the following.

Topical microbicide research and development—Topical 

microbicides are creams, gels, sponges, and other womancontrolled agents that, when used prior to sexual intercourse, 

may help protect women from HIV and other STIs. Although 

microbicides are not yet available for human use, the TransNIH Microbicide Working Group has defined the requirements 

necessary for a safe and effective agent that should both 

protect against acquisition of and prevent transmission of the 

disease. Several candidates are now being studied in clinical 

trials to assess their safety and effectiveness. 

Human papilloma virus (HPV)—Genital HPV is the most 

common STI in the U.S. At least 50 percent of sexually active 

men and women get genital HPV at some time in their lives. 

Although most HPV infections occur and appear to resolve 

without any symptoms or treatment, some types of HPV can 

cause cervical cancer and are the leading causes of cervical 

cancer in women. Recently, the CDC’s Advisory Committee on 

Immunization Practices recommended that a newly licensed 

vaccine designed to protect against HPV routinely be given to 

girls when they are 11–12 years old. National Cancer Institute 

(NCI) scientists and their colleagues, with support from the 

ORWH, worked for two decades to discover the underlying 

causes of cervical cancer and examined ways to boost the 

body’s immune response to prevent the cancer-causing 

infection. Their work led to the development of the technology 

on which the HPV vaccine is based. The NCI is also conducting 

effectiveness trials with a vaccine of their own design. 

To view the videocast of this seminar, visit the NIH Office of Research on Women’s Health Web site at 

http://orwh.od.nih.gov/news/2006.html and select from the list or contact us by telephone at 301-

402-1770. To hear an interview with Alan Hildesheim, M.D., the NCI researcher who worked on the 

development of the HPV vaccine, go to http://orwh.od.nih.gov/ and select Podcast 1.

Science Series

2007

NIH Resources for Health Consumers

More detailed information about STIs may be accessed at: http://cancer.gov/; http://www.niaid.gov/; http://www.nichd.

nih.gov/; http://www.oar.nih.gov/; http://niaaa.gov/; http://nida.gov/; and http://www.nimh.gov/.