CHLAMYDIA THE HIDDEN S.T.D.

What if a disease could secretly invade your organs and prevent you from ever having children--without so much as a telltale sign? That disease is here. It's called chlamydia, and today in the U.S. it's become the most common sexually transmitted disease or STD (an infection that passes from person to person via sexual contact). You may never have heard of chlamydia. Nonetheless, it will infect more than 4 million people this year, according to the Centers for Disease Control and Prevention (CDC). That rate is eight times as great as the infection rate of gonorrhea, the nation's second-most widespread STD.

Health officials had only a murky sense of chlamydia's infection rate until systematic national testing began in 1996. The results are so alarming that doctors now urge sexually active girls to be tested for the disease every six months. (Doctors specify girls because they're more likely than boys to suffer devastating effects without knowing it.) "It's an epidemic of massive proportions," says Dr. Susan DeLisle, an STD expert with the CDC in Atlanta.

INVISIBLE INFECTION

Chlamydia is a bacteria, a microorganism that invades human cells. Like other STDs, it enters the male or female body through sexual contact and the exchange of body fluids, like semen or blood. In most cases chlamydia spreads without symptoms--which is why medical researchers named it from the Greek word for "cloak." "Everything about this disease is like its name: cloaked and secretive," says DeLisle.

Three-quarters of all infected females (and half of infected males) have no idea they're infected, and therefore don't seek treatment, say health officials. Those who do feel the effects typically experience one or more of the following symptoms within weeks of infection:

FEMALES

* any unusual vaginal discharge or bleeding

* burning when urinating

* lower abdominal pain

MALES

* any discharge from penis

* obstructed or painful urine flow

* burning and itching around the penis

* pain and swelling in the testicles

TOLL ON GIRLS

Chlamydia exacts a particularly harsh toll on high-school girls. About half of all cases occur in girls between the ages of 15 and 19. CDC studies show that as many as one in 10 sexually active teenage girls may be infected. Girls who have sex with more than one person face even greater risk.

Why are teenage girls so susceptible? The answer is their reproductive organs, the body parts devoted to producing babies. The uterus, or womb, is shaped like an upside-down pear. Its lower end narrows into a protective opening called the cervix. The immature cervix found in teenage girls is lined with fresh tissue easily subject to infection by chlamydia. "It's possible to get chlamydia when you're older," says DeLisle. "But the teenage cervix is far more vulnerable."

But chlamydia's invasion may not stop at the cervix. It can creep upward to the uterus and fallopian tubes, two spaghetti-size branches that extend like arms to the ovaries, which produce eggs. The damage may go unnoticed for months, or even years. Although a girl will continue to ovulate (produce eggs), she can still be left infertile (unable to have children).

Normally, eggs migrate down the fallopian tubes to the uterus. The eggs may be fertilized (set into reproductive motion) if they encounter sperm, tadpole-shape male sex cells that swim upward. But chlamydia can thwart the process by causing inflammation in the fallopian tubes. The resulting swelling and scarring pinches off the fallopian tubes, just as stepping on a hose blocks the flow of water. Result: Eggs don't reach the sperm or the uterus, and never develop into embryos (the first stage of human development). This condition, known as pelvic inflammatory disease, affects up to 1 million women in the U.S. Half of all PID cases may be due to chlamydia.

STOP THE SPREAD

How can you avoid chlamydia? "Abstinence is the only sure way to avoid an STD," says Marshall Glover, director of the CDC's STD hotline. "Unless they've been tested, you can't know if your partners are infected."

If you think you might be at risk for chlamydia, ask a doctor to administer a urine test. If you're infected, a doctor will prescribe antibiotics, drugs that kill bacteria. But antibiotics won't safeguard you from being reinfected by the same partner, or another. And remember: Birth-control pills may help prevent pregnancies, but they don't protect females from chlamydia and other STDs.

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RELATED ARTICLE: S.T.D.s: Sexually Transmitted Diseases 

    What is it?                           What does it do?

Chlamydia: Bacteria                  Most females have no
common among teens, and a            symptoms. Twenty-five
leading cause of                     percent experience vaginal
infertility (inability               discharges, bleeding, or
to have children).                   abdominal pain. Males
                                     may feel a burning sensation
                                     while urinating.

Gonorrhea: Bacteria                  For females: painful and
that infects the lining of           frequent urination, fever,
females' urethra and cervix.         pelvic pain, vaginal
Like chlamydia, it can result        discharge.
in infertility in women. U.S.        For males: painful urination
location with highest infection      and discharge of puss from
rate for ages 10-24:                 the penis.
Washington, D.C.

Herpes: A permanent viral            Herpes Simplex I causes
infection with recurring             cold sores on the lips and
symptoms. Infections have            face. Genital herpes leads
increased 30 percent in the          to painful genital sores.
last 20 years. As many as 20
percent of Americans carry the
virus that causes genital
herpes.

Human Immunodeficiency               One can be infected with HIV
Virus (HIV): Virus that results      without any symptoms. Once
in AIDS. AIDS, in turn,              HIV progresses to full-blown
renders the body vulnerable          AIDS, the patient may suffer
to infections and cancer. AIDS       weight loss, headaches,
is the sixth leading cause of        fatigue, fever, and swollen
death among people ages              glands. Without a cure, AIDS
15-24 in the U.S.                    is ultimately fatal.

Human Papilloma Virus                Highly contagious warts
(HPV): Virus that causes             start out as small, painless
genital warts. Up to 65              hard spots. They become
percent of people who've             painful as they spread in or
had sex with infected                around the vagina, penis, or
themselves.                          rectum.

Syphilis: Bacteria that              Painless sores on the genitals
remains in the body for life if      or mouth, swollen lymph
left untreated. If the infection     nodes and rashes.
persists, it can cause brain         Most contagious
damage or death. New cases           when sores are
in 1996: 52,995                      present.

    What is it?                           Treatment options

Chlamydia: Bacteria                  Antibiotics, usually
common among teens, and a            tetracycline
leading cause of                     (te-truh-SY-kleen) or
infertility (inability               doxycyline.
to have children).

Gonorrhea: Bacteria                   Antibiotics,
that infects the lining of            usually
females' urethra and cervix.          doxycycline.
Like chlamydia, it can result
in infertility in women. U.S.
location with highest infection
rate for ages 10-24:
Washington, D.C.

Herpes: A permanent viral             No treatment can cure
infection with recurring              herpes, but antiviral drugs
symptoms. Infections have             like acyclovir
increased 30 percent in the           (ay-SY-kloh-vir) help sores
last 20 years. As many as 20          heal.
percent of Americans carry the
virus that causes genital
herpes.

Human Immunodeficiency                There is no cure for AIDS
Virus (HIV): Virus that results       yet, but drugs like AZT can
in AIDS. AIDS, in turn,               slow the progression of the
renders the body vulnerable           virus.
to infections and cancer. AIDS
is the sixth leading cause of
death among people ages
15-24 in the U.S.

Human Papilloma Virus                 No cure exists for the virus
(HPV): Virus that causes              itself. But warts can be
genital warts. Up to 65               treated with medications
percent of people who've              or removed by surgery. In
had sex with infected                 one-third of all cases, warts
themselves.                           return.

Syphilis: Bacteria that               Penicillin injections.
remains in the body for life if
left untreated. If the infection
persists, it can cause brain
damage or death. New cases
in 1996: 52,995