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  • Michael Frey, MD

Sexually Transmitted Infections

What Are STIs and How to Prevent Them

STIs are infections caused by bacteria, viruses, or parasites passed from one person to another during sex, oral, vaginal, or anal sex. Some can also be passed by close skin-to-skin contact. The terms STD and STI are sometimes used to mean the same thing.


  • Genital sores, ulcers, or blisters

  • Oral sores, ulcers, or blisters

  • Vaginal discharge or odor

  • Vaginal pain or burning

  • Pain with urination

  • Pain with sex

  • Fever or chills

  • Sometimes there are no symptoms

Chlamydia Chlamydia is caused by a bacteria called Chlamydia trachomatis and is one of the more common STIs. Symptoms can include:

  • Strong-smelling vaginal discharge

  • Burning when you pee

  • Pain with sex

  • Fever

  • Upset stomach

  • Lower abdominal pain

If untreated, chlamydia can cause pelvic inflammatory disease (PID) as it spreads to the uterus and fallopian tubes, which can cause fever, pain, and infertility.

Chlamydia is treated with antibiotics, start treatment as early as possible to prevent long-term damage.

Gonorrhea You can get it through contact with the mouth, throat, eyes, urethra, vagina, penis, or anus. Over one million cases occur in the United States each year.

Symptoms can be very mild. They include:

  • Burning and pain while urinating

  • Sore throat

  • Painful sexual intercourse

  • Severe pain in the lower abdomen (if the infection spreads to the fallopian tubes and uterus area)

  • Fever (if the infection spreads to the fallopian tubes and uterus area)

  • Abnormal uterine bleeding

  • Bleeding after sex

  • Abnormal vaginal discharge with greenish, yellow or foul smelling discharge

Hepatitis B and C There are several types of hepatitis. Hepatitis B and hepatitis C are transmitted via sex. Hepatitis is a viral disease that leads to swelling or inflammation of the liver.

Hepatitis B has a vaccine for prevention. While hepatitis C doesn’t have a vaccine, treatment is available.

Human Immunodeficiency Virus (HIV) Human immunodeficiency virus (HIV) is the virus that causes acquired immunodeficiency syndrome (AIDS). When a person becomes infected with HIV, the virus attacks and weakens the immune system. As the immune system weakens, the person is at risk of getting life-threatening infections and cancers. When that happens, the illness is called AIDS. Once a person has the virus, it stays inside the body for life.

Human Papillomavirus (HPV) HPV refers to a group of more than 200 viruses, about 40 of which spread via sexual contact. In many cases, HPV resolves on its own, but some HPV viruses can cause cervical, oral, and anal cancer.

If you are sexually active, there is a chance that you have been exposed to the human papillomavirus (HPV). It is a very common sexually transmitted virus that affects approximately 79 million people. It affects people of all ages but is most common among 25- to 35-year-olds.

Herpes Genital herpes is a sexually transmitted disease (STD) spread by skin-to-skin contact. The risk of infection is highest during outbreak periods when there are visible sores and lesions. However, genital herpes can also be transmitted when there are no visible symptoms. Most new cases of genital herpes infection do not cause symptoms, and many people infected with HSV-2 are unaware that they have genital herpes.

There are two forms of HSV:

  • Herpes simplex virus 1 (HSV-1). The usual cause of oral herpes (herpes labialis), which are commonly called cold sores or fever blisters. HSV-1 can also cause genital herpes, which is a sexually transmitted disease (STD).

  • Herpes simplex virus 2 (HSV-2). The usual cause of genital herpes, but it can also cause oral herpes.

Syphilis Syphilis is a bacterial infection usually spread by sexual contact. The disease starts as a painless sore — typically on the genitals, rectum or mouth. Syphilis spreads from person to person via skin or mucous membrane contact with these sores.

After the initial infection, the syphilis bacteria can remain inactive in the body for decades before becoming active again. Early syphilis can be cured, sometimes with a single shot (injection) of penicillin.

Without treatment, syphilis can severely damage the heart, brain or other organs, and can be life-threatening. Syphilis can also be passed from mothers to unborn children.

Mycoplasma Genitalium

Mycoplasma can cause pelvic inflammatory disease (PID). Some of the complications of PID are:

  • Formation of scar tissue that blocks fallopian tubes;

  • Ectopic pregnancy (pregnancy outside the uterus);

  • Infertility (not being able to get pregnant); and

  • Long-term pelvic/abdominal pain.

Pubic Lice Pubic lice (AKA crabs) are parasites that live in pubic hair. They can cause intense itching. You can get pubic lice from skin-to-skin contact, clothes, or bedding. Lice can be treated with lotions that kill the eggs and lice.

Trichomoniasis Trichomoniasis is transmitted during sex. It is also a parasite. The main symptoms include:

  • Green discharge

  • Pain during sex

  • Pain with urination

  • Vaginal odor

  • Burning in the vagina

Prevention Using a condom correctly every time you have sex can help you avoid STDs. Condoms lessen the risk of infection for all STDs.

Testing for STIs Regular STI testing may be a good idea for certain people. If you have a new partner, STI testing along with honest and open communication is key to a safe relationship. If you are in a new relationship or have multiple partners, get tested. Testing before starting a sexual relationship is a good idea.

Practice Safer Sex

  • Wash sex toys

  • Condom use

  • Partner communication

  • Limit sex partners (more partners means a higher risk of contracting STIs)

  • STD testing for your partner and you


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