An Introduction to Sexually Transmitted Infections
Sexually transmitted infections (STIs), once called venereal diseases,
are among the most common infectious diseases in the United States today.
More than 20 STIs have now been identified, and they affect more than
13 million men and women in this country each year. The annual comprehensive
cost of STIs in the United States is estimated to be well in excess
of $10 billion.
Understanding the basic facts about STIs the ways in which they
are spread, their common symptoms, and how they can be treated
is the first step toward prevention. The National Institute of Allergy
and Infectious Diseases (NIAID), a part of the National Institutes of
Health, has prepared a series of fact sheets about STIs to provide this
important information. Research investigators supported by NIAID are
looking for better methods of diagnosis and more effective treatments,
as well as for vaccines and topical microbicides to prevent STIs. It
is important to understand at least five key points about all STDs in
this country today:
- STIs affect men and women of all backgrounds and economic levels.
They are most prevalent among teenagers and young adults. Nearly two-thirds
of all STIs occur in people younger than 25 years of age.
- The incidence of STIs is rising, in part because in the last few
decades, young people have become sexually active earlier yet are
marrying later. In addition, divorce is more common. The net result
is that sexually active people today are more likely to have multiple
sex partners during their lives and are potentially at risk for developing
- Most of the time, STIs cause no symptoms, particularly in women.
When and if symptoms develop, they may be confused with those of other
diseases not transmitted through sexual contact. Even when an STI
causes no symptoms, however, a person who is infected may be able
to pass the disease on to a sex partner. That is why many doctors
recommend periodic testing or screening for people who have more than
one sex partner.
- Health problems caused by STIs tend to be more severe and more frequent
for women than for men, in part because the frequency of asymptomatic
infection means that many women do not seek care until serious problems
When diagnosed and treated early, many STIs can be treated effectively.
Some infections have become resistant to the drugs used to treat them
and now require newer types of antibiotics. Experts believe that having
STIs other than AIDS increases one's risk for becoming infected with
the AIDS virus.
- Some STIs can spread into the uterus (womb) and fallopian tubes
to cause pelvic inflammatory disease (PID), which in turn is a major
cause of both infertility and ectopic (tubal) pregnancy. The latter
can be fatal.
- STIs in women also may be associated with cervical cancer. One
STI, human papillomavirus infection (HPV), causes genital warts
and cervical and other genital cancers.
- STIs can be passed from a mother to her baby before, during, or
immediately after birth; some of these infections of the newborn
can be cured easily, but others may cause a baby to be permanently
disabled or even die.
HIV Infection and AIDS
AIDS (acquired immunodeficiency syndrome) was first reported in the
United States in 1981. It is caused by the human immunodeficiency virus
(HIV), a virus that destroys the body's ability to fight off infection.
An estimated 900,000 people in the United States are currently infected
with HIV. People who have AIDS are very susceptible to many life-threatening
diseases, called opportunistic infections, and to certain forms of cancer.
Transmission of the virus primarily occurs during sexual activity and
by sharing needles used to inject intravenous drugs. If you have any
questions about HIV infection or AIDS, you can call the AIDS Hotline
confidential toll-free number: 1-800-342-AIDS.
This infection is now the most common of all bacterial STIs, with an
estimated 4 to 8 million new cases occurring each year. In both men
and women, chlamydial infection may cause an abnormal genital discharge
and burning with urination. In women, untreated chlamydial infection
may lead to pelvic inflammatory disease, one of the most common causes
of ectopic pregnancy and infertility in women. Many people with chlamydial
infection, however, have few or no symptoms of infection. Once diagnosed
with chlamydial infection, a person can be treated with an antibiotic.
Genital herpes affects an estimated 60 million Americans. Approximately
500,000 new cases of this incurable viral infection develop annually.
Herpes infections are caused by herpes simplex virus (HSV). The major
symptoms of herpes infection are painful blisters or open sores in the
genital area. These may be preceded by a tingling or burning sensation
in the legs, buttocks, or genital region. The herpes sores usually disappear
within two to three weeks, but the virus remains in the body for life
and the lesions may recur from time to time. Severe or frequently recurrent
genital herpes is treated with one of several antiviral drugs that are
available by prescription. These drugs help control the symptoms but
do not eliminate the herpes virus from the body. Suppressive antiviral
therapy can be used to prevent occurrences and perhaps transmission.
Women who acquire genital herpes during pregnancy can transmit the virus
to their babies. Untreated HSV infection in newborns can result in mental
retardation and death.
Genital warts (also called venereal warts or condylomata acuminata)
are caused by human papillomavirus, a virus related to the virus that
causes common skin warts. Genital warts usually first appear as small,
hard painless bumps in the vaginal area, on the penis, or around the
anus. If untreated, they may grow and develop a fleshy, cauliflower-like
appearance. Genital warts infect an estimated 1 million Americans each
year. In addition to genital warts, certain high-risk types of HPV cause
cervical cancer and other genital cancers. Genital warts are treated
with a topical drug (applied to the skin), by freezing, or if they recur,
with injections of a type of interferon. If the warts are very large,
they can be removed by surgery.
Approximately 400,000 cases of gonorrhea are reported to the U.S. Centers
for Disease Control and Prevention (CDC) each year in this country.
The most common symptoms of gonorrhea are a discharge from the vagina
or penis and painful or difficult urination. The most common and serious
complications occur in women and, as with chlamydial infection, these
complications include PID, ectopic pregnancy, and infertility. Historically,
penicillin has been used to treat gonorrhea, but in the last decade,
four types of antibiotic resistance have emerged. New antibiotics or
combinations of drugs must be used to treat these resistant strains.
The incidence of syphilis has increased and decreased dramatically
in recent years, with more than 11,000 cases reported in 1996. The first
symptoms of syphilis may go undetected because they are very mild and
disappear spontaneously. The initial symptom is a chancre; it is usually
a painless open sore that usually appears on the penis or around or
in the vagina. It can also occur near the mouth, anus, or on the hands.
If untreated, syphilis may go on to more advanced stages, including
a transient rash and, eventually, serious involvement of the heart and
central nervous system. The full course of the disease can take years.
Penicillin remains the most effective drug to treat people with syphilis.
Other diseases that may be sexually transmitted include trichomoniasis,
bacterial vaginosis, cytomegalovirus infections, scabies, and pubic
STDs in pregnant women are associated with a number of adverse outcomes,
including spontaneous abortion and infection in the newborn. Low birth
weight and prematurity appear to be associated with STDs, including
chlamydial infection and trichomoniasis. Congenital or perinatal infection
(infection that occurs around the time of birth) occurs in 30 to 70
percent of infants born to infected mothers, and complications may include
pneumonia, eye infections, and permanent neurologic damage.
What Can You Do to Prevent STIs?
The best way to prevent STDs is to avoid sexual contact with others.
If you decide to be sexually active, there are things that you can do
to reduce your risk of developing an STD.
- Have a mutually monogamous sexual relationship with an uninfected
- Correctly and consistently use a male condom.
- Use clean needles if injecting intravenous drugs.
- Prevent and control other STDs to decrease susceptibility to HIV
infection and to reduce your infectiousness if you are HIV-infected.
- Delay having sexual relations as long as possible. The younger people
are when having sex for the first time, the more susceptible they
become to developing an STD. The risk of acquiring an STD also increases
with the number of partners over a lifetime.
Anyone who is sexually active should:
- Have regular checkups for STIs even in the absence of symptoms,
and especially if having sex with a new partner. These tests can be
done during a routine visit to the doctor's office.
- Learn the common symptoms of STIs. Seek medical help immediately
if any suspicious symptoms develop, even if they are mild.
- Avoid having sex during menstruation. HIV-infected women are probably
more infectious, and HIV-uninfected women are probably more susceptible
to becoming infected during that time.
- Avoid anal intercourse, but if practiced, use a male condom.
- Avoid douching because it removes some of the normal protective
bacteria in the vagina and increases the risk of getting some STIs.
Anyone diagnosed as having an STI should:
- Be treated to reduce the risk of transmitting an STI to an infant.
- Discuss with a doctor the possible risk of transmission in breast
milk and whether commercial formula should be substituted.
- Notify all recent sex partners and urge them to get a checkup.
- Follow the doctor's orders and complete the full course of medication
prescribed. A follow-up test to ensure that the infection has been
cured is often an important step in treatment.
- Avoid all sexual activity while being treated for an STI.
Sometimes people are too embarrassed or frightened to ask for help
or information. Most STIs are readily treated, and the earlier a person
seeks treatment and warns sex partners about the disease, the less likely
the disease will do irreparable physical damage, be spread to others
or, in the case of a woman, be passed on to a newborn baby.
Private doctors, local health departments, and STD and family planning
clinics have information about STIs. In addition, the American Social
Health Association (ASHA) provides free information and keeps lists
of clinics and private doctors who provide treatment for people with
STIs. ASHA has a national toll-free telephone number, 1-800-227-8922.
The phone number for the Herpes Hotline, also run by ASHA, is 919-361-8488.
Callers can get information from the ASHA hotline without leaving their
STIs cause physical and emotional suffering to millions and are costly
to individuals and to society as a whole. NIAID conducts and supports
many research projects designed to improve methods of prevention, and
to find better ways to diagnose and treat these diseases. NIAID also
supports several large university-based STI research centers.
Within the past few years, NIAID-supported research has resulted in
new tests to diagnose some STDs faster and more accurately. New drug
treatments for STIs are under investigation by NIAID researchers. This
is especially important because some STIs are becoming resistant to
the standard drugs. In addition, vaccines are being developed or tested
for effectiveness in preventing several STIs, including AIDS, chlamydial
infection, genital herpes, and gonorrhea.
It is up to each individual to learn more about STIs and then make
choices about how to minimize the risk of acquiring these diseases and
spreading them to others. Knowledge of STIs, as well as honesty and
openness with sex partners and with one's doctor, can be very important
in reducing the incidence and complications of sexually transmitted
Sexually Transmitted Diseases and the Organisms
NIAID is a component of the National Institutes of Health
(NIH), which is an agency of the Department of Health and Human Services.
NIAID supports basic and applied research to prevent, diagnose, and
treat infectious and immune-mediated illnesses, including HIV/AIDS
and other sexually transmitted diseases, illness from potential agents
of bioterrorism, tuberculosis, malaria, autoimmune disorders, asthma
News releases, fact sheets and other NIAID-related
materials are available on the NIAID Web site at http://www.niaid.nih.gov.
Office of Communications and Public Liaison
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Bethesda, MD 20892
Last Updated November 21, 2003 (alt)