Sexually transmitted infections are diseases spread by sexual contact. Some of the most common STIs are:

• Chlamydia.
• Genital herpes.
• Genital warts or human papillomavirus (HPV).
• Gonorrhea.
• Hepatitis B.
• Human immunodeficiency virus (HIV), which causes AIDS.
• Syphilis.
• Trichomoniasis.

Left untreated, some STIs can lead to serious problems. For example:

• Certain high-risk types of HPV can cause cervical cancer in women, penile cancer in men, and rectal and oral cancer in men and women.
• Some STIs can be passed from a woman to her newborn, which can cause serious problems for the baby.
• Chlamydia and gonorrhea can cause pelvic inflammatory disease (PID) in women. PID can lead to serious problems, including not being able to have a baby (infertility).
• Syphilis can cause problems with pregnancy, nerve and heart problems, and death.
• Gonorrhea can increase the risk of bladder cancer in men.

Treatment is available for all sexually transmitted infections (STIs) to relieve symptoms, even if a cure isn't possible.

Some of the most common STIs—chlamydia, gonorrhea, and syphilis—are caused by bacteria and are treated and cured with antibiotics.

STIs caused by viruses, such as genital herpes and genital warts, aren't cured with antibiotics. But treatments are available to relieve symptoms.

Having a routine STI test means getting tested even though you don't have symptoms of an infection. Experts say that certain groups should be routinely tested for certain STIs. Some expert opinions may vary, and your doctor may recommend testing based on your personal history.

Chlamydia

The Public Health Agency of Canada (PHAC) recommends a chlamydia test for sexually active men and women younger than 25 and all pregnant women.^{footnote 3}

You have an increased risk of getting chlamydia if:^{footnote 3}

• You have had sex with someone who has chlamydia.
• You've had chlamydia or other STIs before.
• You have a new sex partner or have had more than two sex partners in the past year.
• You are an injection drug user, in prison or jail, a sex worker, or a street youth.

Gonorrhea

Talk to your doctor about whether you need routine testing for gonorrhea.

You have an increased risk of getting gonorrhea if:^{footnote 1}

• You have had sex with someone who has gonorrhea or who is at risk for gonorrhea.
• You have unprotected sex with a person from an area with a high rate of gonorrhea.
• You travel to an area with a high rate of gonorrhea and have unprotected sex with some who lives there.
• You're a sex worker or have sex with sex workers.
• You're a sexually active male or female younger than 25 and have more than one partner.
• You're a street-involved youth.
• You are a man who has unprotected sex with men.
• You have had gonorrhea or another STI before.

Syphilis

The PHAC recommends a syphilis test for all pregnant women.^{footnote 2}

You have an increased risk of getting syphilis if you:^{footnote 2}

• Have had sex with someone who has syphilis.
• Are a man who has sex with men.
• Are a sex worker.
• Have street involvement or are homeless.
• Use injection drugs.
• Have more than one sex partner.
• Have HIV or have had syphilis or other STI's before.
• Are from a country or have sex with a person from a country with a high rate of syphilis.
• Have sex with a person with any of the risks above.

Tests for STIs are fairly simple. If you have a test for chlamydia or gonorrhea, a nurse or doctor will test for bacteria that cause the infections. You may have a urine test, or the doctor may take a sample of body fluid from the throat, inside the tip of the penis, or inside the rectum or vagina. A gonorrhea culture test also may be done to see if the bacteria are resistant to antibiotics.

A syphilis test looks for antibodies to the bacteria that cause syphilis. Your doctor may do a blood test or may test body fluid or tissue. A follow-up test may be done to confirm the infection.

Getting tested can help find an infection early or when you have no symptoms. This is important so that:

• You can get treatment and avoid long-term problems, such as not being able to have a baby (infertility).
• If you know that you have an STI, you can get treatment and avoid spreading the infection to others.
• If you know that you have an STI, you can tell your sex partner(s) so they can be treated and can avoid spreading the infection.
• If you're pregnant, an STI test can find an infection so you don't spread the infection to your newborn.

• If your test shows that you have an STI, your sex partner(s) will need to know and get tested, which may affect your relationship.
• If you have an STI, your doctor may be required by law to report it to your local health unit. You may be asked for names and addresses of your sex partners.
• You could have a false-positive test result, which shows that you have the disease when you actually don't. This could cause you unneeded worry and treatment.
• For syphilis, you could have a false-negative result, which shows that you don't have the disease when you actually do. (Sometimes the test can't find the antibodies yet.) So you might infect others because you don't think you have the disease.

Your doctor may want you to be tested if:

• You have a high risk for getting an STI.
• You are pregnant.