Sexually Transmitted Diseases
On this page:
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
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 STIs.
- 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 have developed.
- 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
- 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.
- 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
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.
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
sharing needles used to inject intravenous drugs.
Return to top
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.
Return to top
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.
Return to top
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.
Return to top
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
Return to top
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
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.
Return to top
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 partner.
- 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 names.
Return to top
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
Return to top