Sexually Transmitted
Infections (STIs), formerly known as venereal diseases, more
than 25 infections passed from one person to another primarily during sexual
contact. STIs are among the most common infections known—more than 15 million
people become infected with one or more STIs every year. The States has the highest STI rate in the
industrialized world—roughly half of all Americans become infected with an STI
before the age of 35. While Nigeria has the highest in Africa. Despite the
prevalence of STIs, studies show that many people are unaware of their risks
for contracting an STI or the serious, and sometimes deadly, health
consequences that may result from an untreated infection.
Some STIs, such as gonorrhea
or chlamydia, may cause no symptoms. People who do not know they are infected
risk infecting their sexual partners and, in some cases, their unborn children.
If left untreated, these diseases may cause debilitating pain or may destroy a
woman’s ability to have children. Some STIs can be cured with a single dose of
antibiotics, but many, such as acquired immunodeficiency syndrome (AIDS), are
incurable. People with these diseases remain infectious to others for their
entire lives.
Those most at risk for
contracting STIs are people who have unprotected sex—that is, sex without using
a latex or polyurethane condom; those who have multiple partners; and those
whose sex partners include intravenous drug users who share needles. Studies
show that Americans between the ages of 16 and 24 are at greater risk for
acquiring STIs than are older adults because younger people are more likely to
have multiple sexual partners rather than a single, long-term relationship.
Additionally, young people may be more likely to have unprotected sex and they
may find it difficult to tell their sexual partners they are infected with an
STI. Young people may also be embarrassed or unable to seek treatment for STIs.
This means that they are not only more likely to pass the disease to other
young people, they also have a greater risk of suffering the long-term
consequences of untreated STIs.
HOW
STIS ARE TRANSMITTED
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Placenta
The placenta is responsible for respiration
and excretion in the growing fetus. Fetal blood flows through the blood vessels
of the umbilical cord to the placenta, where fingerlike capillary nets are
surrounded by pools of the mother’s blood. Here carbon dioxide and other
metabolic wastes diffuse from fetus to mother, and oxygen and nutrients pass
from mother to fetus. Some STDs can be passed from an infected mother to her
unborn child when disease-causing organisms cross the placenta.
STIs are transmitted by
infectious agents—microscopic bacteria, viruses, parasites, fungi, and
single-celled organisms called protozoa—that thrive in warm, moist environments
in the body, such as the genital area, mouth, and throat. Most STIs spread
during sexual intercourse (vaginal or anal), but other forms of sexual contact,
such as oral sex, can also spread disease.
Some STIs are transmitted
in ways other than by sexual contact. Certain viral STIs, such as AIDS and some
types of hepatitis, may be transmitted by contact with infected blood. For
instance, viral STIs may pass between people who share infected needles, and a
person can become infected from a transfusion of infected blood. Some STIs may
pass from an infected mother to her child. Infection may occur before birth,
when the infectious agent crosses the placenta (organ in a pregnant woman’s
uterus that links the blood supplies of mother and baby) and enters the baby’s
bloodstream. Infection also may occur during childbirth, as the baby passes
through the birth canal, or after birth, when the baby consumes infected breast
milk. STIs cannot be transmitted through shaking hands or other casual contact,
or through contact with inanimate objects such as clothing or toilet seats.
COMMON STIS
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The most common STIs include
chlamydia, gonorrhea, syphilis, herpes, AIDS, hepatitis, genital warts, and
trichomoniasis.
Chlamydia
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According to the Centers
for Disease Control and Prevention (CDC), chlamydia is the most frequently
reported infectious disease. Caused by the Chlamydia trachomatis bacterium,
the disease does not produce noticeable symptoms in 75 percent of women and 50
percent of men, so an infection often goes undiagnosed. Experts estimate that 3
million people become infected with chlamydia each year, but according to the
CDC, only about 660,000 of these infections are reported each year.
People who do not know
they are infected with chlamydia may not seek medical care and they may
continue to have sex, unknowingly spreading the disease. When symptoms do
develop, men may experience painful or burning urination or a discharge from
the penis. Women may experience bleeding between periods, burning urination,
vaginal discharge, or mild lower abdominal pain. If left untreated in women,
chlamydia can cause severe health problems. Chlamydia damages female
reproductive tissue, causing pelvic inflammatory disease (PID). PID can cause
chronic, debilitating pelvic pain, infertility, or fatal pregnancy
complications. Babies born to mothers infected with chlamydia are at risk of
developing eye and lung infections.
Diagnosing chlamydia infections
requires a physical examination in which a health-care provider performs a
pelvic examination to collect a small amount of vaginal or penile fluid, which
is then tested for the presence of Chlamydia trachomatis. New diagnostic
tests that use urine samples to identify the presence of the chlamydia bacteria
have become available, providing a noninvasive way to diagnose people who show
no symptoms for the disease. Chlamydia is treatable with antibiotics.
Gonorrhea
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Gonorrhea, caused by the
bacterium Neisseria gonorrhoeae, infects the membranes lining certain
genital organs. Although roughly 360,000 gonorrhea infections are reported each
year, Experts estimate that closer to 650,000 people are infected annually.
Like chlamydia, gonorrhea is often symptomless. When present, symptoms may be
similar to those of chlamydia and include burning urination and penile or
vaginal discharge. Untreated gonorrhea can cause PID in women. Babies born to
mothers with gonorrhea are at risk of infection during childbirth; such
infections can cause eye disease in the newborn. Physicians diagnose gonorrhea
by testing penile or vaginal discharge or urine specimens for the presence of Neisseria
gonorrhoeae. Gonorrhea is treatable with several antibiotics, although the
infection has become resistant to treatment with some drugs in the past several
decades.
Syphilis
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Syphilis, a potentially
life-threatening STI, is caused by the bacterium Treponema pallidum.
According to the CDC, there are an estimated 36,000 new cases of syphilis each year.
In the early stage of syphilis, a genital sore, called a chancre, develops
shortly after infection and eventually disappears on its own. If the disease is
not treated, the infection can progress over years, affecting the vertebrae,
brain, and heart, and resulting in such varied disorders as lack of
coordination, meningitis, and stroke. Syphilis during pregnancy can be
devastating to the fetus, causing deformity and death, and most pregnant women receive
screening for the disease in the first weeks of pregnancy so that the disease
can be treated before the fetus is harmed. Syphilis is easily treated with
penicillin, and the number of cases has dropped considerably since 1982. By the
late 1990s, however, many urban communities experienced a resurgence in
syphilis cases among men who have sex with men.
Genital
Herpes
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Genital herpes is caused
by infection with the herpes simplex virus (HSV). Most cases of genital herpes
are due to HSV type 2. Some cases, however, result from genital infections with
HSV type 1, a common cause of cold sores. Genital herpes causes recurrent
outbreaks of painful sores on the genitals, although the disease often remains
dormant with no symptoms for long periods. In the United States, one in five
individuals over the age of 12 is infected with HSV type 2, and the vast
majority of those infected—about 90 percent—do not know they have the disease.
Blood tests can detect HSV infection, even if a person has no symptoms. The
symptoms of HSV can be treated with antiviral drugs, such as acyclovir, but HSV
cannot be eradicated from the body—it is incurable.
AIDS
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A Global Epidemic
More than 42 million people around the world
are currently infected with human immunodeficiency virus (HIV), the virus that
causes acquired immunodeficiency syndrome (AIDS). New HIV infections have
leveled off or even declined in most developed countries, but the virus is
spreading rapidly through much of the developing world. In some areas of
sub-Saharan Africa, one in four adults is carrying the virus.
AIDS, the result of infection
with the human immunodeficiency virus (HIV), is an incurable and deadly STI.
AIDS attacks the body’s immune system, leaving victims unable to fight off even
the mildest infections. While HIV can be transmitted by other means, sexual
contact is the most common means of transmission. Women who are infected with
HIV can pass the virus to their infants during pregnancy, childbirth or, less
frequently, in breast milk. Treatment options for people infected with HIV
include protease inhibitors, which can markedly increase survival. In spite of
widespread educational and prevention programs, the CDC estimates that there
are 40,000 new cases of HIV each year in the United States and that 800,000 to
900,000 Americans overall have HIV infection.
Hepatitis B Virus
The hepatitis B virus (HBV) is passed from
person to person through contaminated body fluids. Although transmission can
occur in many ways, the most important mode of transmission is sexual contact.
One hundred times more
contagious than HIV, hepatitis B passes from person to person through
unprotected sexual intercourse with an infected person, or through the sharing
of infected needles or other sharp instruments that break the skin. Hepatitis B
can also spread during childbirth: Between 90 and 95 percent of all babies born
to infected mothers get the disease during birth. The CDC estimates that
120,000 new hepatitis B infections occur each year. Hepatitis B attacks liver
cells, sometimes leading to cirrhosis and cancer of the liver. In most cases
hepatitis B is incurable, but arduous chemotherapy can eliminate the virus in
some patients. There is a safe, effective vaccination for hepatitis B, and most
states are developing or already have initiated public school immunization
programs.
Genital Warts
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Genital warts grow on
the penis and in and around the entrance to the vagina and anus. They are
caused by a family of viruses known as human papillomavirus (HPV) that are
transmitted during sexual intercourse. The CDC estimates that there are 5.5
million new cases of genital warts each year. Genital warts are treatable with
topical medications and can be removed with minor surgical procedures. Certain
types of HPV that cause genital infections can also cause cervical cancer.
Regular pap smear screenings can detect abnormalities at an early stage, when
they can more easily be treated to prevent cancer developing. The first vaccine
against HPV strains that can cause genital warts and cervical cancer was
approved by the U.S. Food and Drug Administration and by Health Canada in 2006.
Sold under the brand name Gardasil, the new vaccine completely prevented
infections in women in nearly all clinical trials.
Trichomoniasis
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Trichomoniasis, caused by
infection with the protozoan Trichomonas vaginalis, causes burning,
itching, and discomfort in the vagina in women and the urethra in men.
Trichomoniasis is easily treated with a single dose of antibiotics. The CDC
estimates that 5 million Americans become infected with trichomoniasis each
year.
PREVENTION AND CONTROL
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Unlike many serious diseases,
simple measures can prevent STIs. The most effective prevention method is
abstinence—that is, refraining from sex completely. No sexual contact means no
risk of developing an STI. Practicing monogamy, in which two partners do not
have sexual relations with anyone but each other, also greatly reduces the risk
of spreading and contracting STIs.
Latex condoms are an effective,
although not perfect, form of protection from STIs. These plastic sheaths, worn
over the penis or inserted into the vagina, act as a physical barrier to
organisms that cause STIs. However, condoms do not cover all of the genital
surfaces that may come into contact during sex, and the possibility of
transmission of some STIs, especially genital herpes and warts, still exists.
Early diagnosis and thorough
treatment prevent the more serious consequences of STI infection, while halting
the spread of STIs from person to person. This is most critical in STIs that do
not cause symptoms, because those infected often do not know they risk
infecting their sexual partners. The complete dosage of drug treatment must be
completed, even if early doses of drugs appear to alleviate symptoms entirely.
The infection may still persist in the absence of symptoms, leading infected
individuals to unknowingly spread the disease.
Public clinics screen
patients at risk for STIs in order to diagnose and treat diseases in the early
stages. Clinics track the incidence of STIs in particular areas and contact the
sexual partners of infected individuals. By identifying and treating these
potential carriers, clinics are able to break the chain of STI infections.
Several organizations, such as the CDC and the World Health Organization,
monitor and research the prevalence and transmission of STIs on an
international level in an effort to prevent local outbreaks from reaching
global, epidemic proportions.
TRENDS IN STIS
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At any time in history,
the prevalence and significance of different STIs mirror changes in science and
society. For example, in many countries of the world, the incidence of STIs
increased during and immediately after World War II (1939-1945), when soldiers
spending extended periods of time away from home engaged in unprotected sexual
relations with different partners, many of whom carried STIs. When the
antibiotic penicillin became widely available in the following years, the same
countries experienced dramatic reductions in STI incidence. Beginning in the
1950s, however, the incidence of gonorrhea began to rise as American sexual
mores changed. Strains of the disease developed resistance to penicillin, and
by the 1970s and 1980s the disease reached epidemic proportions in young adult
populations. Introduction of HIV into the human population led to an
international AIDS crisis that began in the 1980s and continues to this day.
Cases of STIs are increasing,
even though the use of condoms has increased since the onset of the AIDS
epidemic. Public health officials believe that many factors are probably
responsible for the increase in STIs, among them trends in sexual behavior. In
the last several decades, the age at which people have sex for the first time
has shifted downward, while the average number of partners a person has sex
with during his or her lifetime has increased. Together, these trends increase
the risk of exposure to an STI.
