Chlamydia is an infection that you can get through sexual contact. It is caused by bacteria called Chlamydia trachomatis. The CDC says chlamydia is the most commonly reported sexually transmitted infection (STI) caused by bacteria. But many cases may be missed. That's because most people don't know they have it. The infection may have few symptoms in the early stages.

Anyone who has sex is at risk for chlamydia. Young adults are at very high risk. They may be less likely to use condoms during sex. Some young adults may also not have access to STI prevention care. They may be more likely to have more than one sex partner, including partners who have chlamydia.

Young women also may have cervical ectopy. Cervical ectopy means that the layer of cells lining the cervical canal extends to the outer layer of the cervix. This raises their risk for chlamydia.

Practicing safe sex may help prevent chlamydia. Men and women can spread this disease by having unprotected sex. This includes vaginal, oral, or anal sex. You can lower your risk by not having sex. Or if you do have sex, you can lower your risk by limiting the number of sex partners you have.

You can also lower your risk by using condoms and by using a dental dam during oral sex. Don't have sex with an infected person until they are done with treatment. If you have chlamydia, all your sex partners from the last 60 days should be tested. They should be treated for the disease if they test positive for it. Women are often infected again if their sex partners aren't treated.

Gay, bisexual, and other men who have sex with men and transgender women and are at high risk of STIs can lower their risk of chlamydia by taking a single two-pill dose of the antibiotic doxycycline within 72 hours after unprotected sex. This is called "Doxycycline Post-Exposure Prophylaxis (Doxy PEP)". Ask your doctor if DoxyPEP might be a good choice for you.

Most people with chlamydia have no symptoms. An early sign of the disease in people assigned female at birth is a mucous-like vaginal discharge. But they may not notice this because many people have different amounts of discharge from day to day. These are other symptoms:

• Pain or burning when urinating
• Frequent urination
• Abnormal vaginal discharge
• Pain in the lower belly or lower back
• Nausea
• Fever
• Bleeding between menstrual periods
• Painful intercourse

Symptoms that people assigned male at birth with chlamydia may have:

• Discharge from penis
• Frequent urination
• Pain or burning when urinating
• Watery or mucus discharge
• Painful, swollen testicles

People can also get infected with chlamydia in their rectum. This happens by having anal sex. Or it can be spread from another infected site, such as the vagina. These infections often have no symptoms, but they can cause:

• Rectal pain
• Discharge
• Bleeding

Chlamydia in people assigned female at birth can spread into the uterus and fallopian tubes if not treated. It can cause pelvic inflammatory disease (PID). Possible complications from PID include:

• Long-term pelvic pain
• Infertility
• Ectopic pregnancy (tubal pregnancy). This happens when a fertilized egg implants in the fallopian tube instead of in the uterus. These pregnancies must be ended to save the birth parent's life. This often needs surgery.

Chlamydia during pregnancy can affect the baby. These are some possible effects:

• Premature birth
• Low birth weight
• Infections, such as eye infection (conjunctivitis) and pneumonia

People assigned male at birth who have untreated chlamydia can get:

• Infection of the genital tract
• Infection of the prostate
• Reactive arthritis
• Conjunctivitis

For people who have anal sex, chlamydia can cause an infection of the rectal area. Certain strains of chlamydia can cause lymphogranuloma venereum (LGV). This health problem most often affects the rectal area. It causes bleeding, pain, or discharge, and can lead to abscesses and damage to tissue (fistulas).

All people with chlamydia are also at greater risk of getting HIV if they are exposed to someone with the virus.

If you are diagnosed with chlamydia, you can quickly cure the disease with treatment. But most people with it have mild symptoms or none at all. That is why many people don't know they have chlamydia.

Chlamydia can now be easily tested for with a urine sample, vaginal swab, rectal swab, or throat swab. Many women now have chlamydia tests done on the same sample used to do a Pap test.

Chlamydia is treated with antibiotics. The most common and effective treatment is a 7-day course of doxycycline. A single dose of azithromycin may be given, but it is less effective than 7 days of doxycycline. For LGV, you need 21 days of doxycycline treatment.

All sex partners should be checked, tested, and treated. If you have chlamydia, don't have sex until you and your sex partners are done with treatment. If not, you may get infected again. Wait 1 week after taking the 1-dose azithromycin. You can start having sex again the day after finishing treatment with the 7-day or 21-day course of doxycycline.

Widespread screening is a good way to diagnose and treat chlamydia. The CDC and the Office of Population Affairs have started many screening programs. The CDC recommends screening every year for all sexually active people ages 24 and under. It also recommends yearly screenings for older people who have one or more risk factors. Risk factors include having more than one sex partner and not using a condom. Pregnant people should always be screened for chlamydia. All likely exposed body sites should be screened, such as the vagina and rectum.

People who have anal sex should be screened regularly for chlamydia at all exposed body sites.