Sexually transmitted diseases (STDs) WORLD OF MICROBIOLOGY AND IMMUNOLOGY512•
also noted that sexually transmitted disease appears to
increase in areas where AIDS is common.
Shifting sexual and marital habits are two factors behind
the growth in sexually transmitted disease. Americans are
more likely to have sex at an earlier age than they did in years
past. They also marry later in life than Americans did two to
three decades ago, and their marriages are more likely to end
in divorce. These factors make Americans more likely to have
many sexual partners over the course of their lives, placing
them at greater risk of sexually transmitted disease.
Public health officials report that fear and embarrass-
ment continue to limit the number of people willing to report
signs of sexually transmitted disease.
All sexually transmitted diseases have certain elements
in common. They are most prevalent among teenagers and
young adults, with nearly 66% occurring in people under 25.
In addition, most can be transmitted in ways other than
through sexual relations. For example, AIDS and Hepatitis B
can be transmitted through contact with tainted blood, but they
are primarily transmitted sexually. In general, sexual contact
should be avoided if there are visible sores, warts, or other
signs of disease in the genital area. The risk of developing
most sexually transmitted diseases is reduced by using con-
doms and limiting sexual contact—but can only be reduced to
zero by having monogamous (one partner) sexual relations
between partners who are free of disease or vectors of disease
(e.g., the HIV virus).
Bacterial sexually transmitted diseases include
syphilis, gonorrhea, chlamydia, and chancroid. Syphilis is
less common than many other sexually transmitted diseases
in the Unites States, with 134,000 cases in 1990. The disease
is thought to be more difficult to transmit than many other
sexually transmitted diseases. Sexual partners of an individ-
ual with syphilis have about a 10% chance of developing
syphilis after one sexual contact, but the disease has come
under increasing scrutiny as researchers have realized how
easily the HIV virus which causes AIDS can be spread
through open syphilitic chancre sores.
Gonorrhea is far more common than syphilis, with
approximately 750,000 cases of gonorrhea reported annually
in the United States. The gonococcus bacterium is considered
highly contagious. Public health officials suggest that all indi-
viduals with more than one sexual partner should be tested
regularly for gonorrhea. Penicillin is no longer the treatment
of choice for gonorrhea, because of the numerous strains of
gonorrhea that are resistant to penicillin. Newer strains of
antibioticshave proven to be more effective. Gonorrhea infec-
tion overall has diminished in the United States, but the inci-
dence of gonorrhea among certain populations (e.g.,
African-Americans) has increased.
Chlamydia infection is considered the most common
sexually transmitted disease in the United States. About four
million new cases of chlamydia infection are reported every
year. The infection is caused by the bacterium Chlamydia tra-
chomatis. Symptoms of chlamydia are similar to symptoms of
gonorrhea, and the disease often occurs at the same time as
gonorrhea. Men and women may have pain during urination or
notice an unusual genital discharge one to three weeks afterexposure. However, many individuals, particularly women,
have no symptoms until complications develop.
Complications resulting from untreated chlamydia
occur when the bacteria has a chance to travel in the body.
Chlamydia can result in pelvic inflammatory disease in
women, a condition which occurs when the infection travels
up the uterus and fallopian tubes. This condition can lead to
infertility. In men, the infection can lead to epididymitis,
inflammation of the epididymis, a structure on the testes
where spermatozoa are stored. This too can lead to infertility.
Untreated chlamydia infection can cause eye infection or
pneumoniain babies of mothers with the infection. Antibiotics
are successful against chlamydia.
The progression of chancroid in the United States is a
modern-day indicator of the migration of sexually transmitted
disease. Chancroid, a bacterial infection caused by
Haemophilus ducreyi, was common in Africa and rare in the
United States until the 1980s. Beginning in the mid-1980s,
there were outbreaks of chancroid in a number of large cities
and migrant-labor communities in the United States. The num-
ber of chancroid cases increased dramatically during the last
two decades of the twentieth century.
In men, who are most likely to develop chancroid, the
disease is characterized by painful open sores and swollen
lymph nodes in the groin. The sores are generally softer than
the harder chancre seen in syphilis. Women may also develop
painful sores. They may feel pain urinating and may have
bleeding or discharge in the rectal and vaginal areas.
Chancroid can be treated effectively with antibiotics.
As of June 2002, there are no cures for the sexually
transmitted diseases caused by viruses: AIDS, genital herpes,
viral hepatitis, and genital warts. Treatment to reduce adverse
symptoms is available for most of these diseases, but the virus
cannot be eliminated from the body.
AIDS is the most life-threatening sexually transmitted
disease, a disease which is usually fatal and for which there is
no cure. The disease is caused by the human immunodefi-
ciency virus(HIV), a virus which disables the immune sys-
tem, making the body susceptible to injury or death from
infection and certain cancers. HIV is a retrovirus which trans-
lates the RNAcontained in the virus into DNA, the genetic
information code contained in the human body. This DNA
becomes a part of the human host cell. The fact that viruses
become part of the human body makes them difficult to treat
or eliminate without harming the patient.
HIV can remain dormant for years within the human
body. More than 800,000 cases of AIDS have been reported in
the United States Centers for Disease Controlsince the disease
was first identified in 1981, and at least one million other
Americans are believed to be infected with the HIV virus.
Initial symptoms of AIDS include fever, headache, or enlarged
lymph nodes. Later symptoms include energy loss, frequent
fever, weight loss, or frequent yeastinfections. HIV is trans-
mitted most commonly through sexual contact or through use
of contaminated needles or blood products. The disease is not
spread through casual contact, such as the sharing of towels,
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