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Types of STIs

Sexually transmitted infections (STIs) are infections that you can get by having vaginal, oral, or anal sex with someone who already has an STI. You can also possibly get them from skin-to-skin contact between genitals. STIs are also sometimes called sexually transmitted diseases, or STDs. Whatever you call them, though, they can cause serious health problems. And they happen a lot to young people: Almost half of new infections are among people ages 15 to 24.

There are more than 25 different STIs caused by many types of bacteria and viruses. Each STI has its own symptoms, but some infections have similar symptoms. One thing is clear, though. If you get an unusual discharge, sore, or rash, especially in the pubic area, you should stop having sex and see a doctor right away.

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Image of lots of faces to indicate how many people can have sex with eachother and pass on diseases.

One partner can expose you to many diseases. You are at risk of getting all of the STIs that your partner's past and present partners have had.

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Check out the symptoms, tests, and treatments for common STIs below.

What is it?

Chlamydia (say: kluh-MID-ee-uh) is a very common STI caused by a bacteria. Women who have chlamydia are much more likely to get HIV if they are exposed to it.

Also, if it’s not treated, chlamydia can cause serious problems, like not being able to have a baby.

What are some symptoms?

Because chlamydia often doesn’t cause symptoms, experts recommend that teens who have sex get tested for it every year.

Symptoms can include:

  • Unusual vaginal discharge (not the clear or slightly white fluid women often have)
  • Burning when urinating
  • Bleeding between periods
  • Stomach pain
  • Back pain
  • Nausea
  • Fever
  • Pain during sex
How could you get it?It is passed through vaginal, anal, or oral sex. A mother also can pass it to her baby when it goes through her vagina.
How do you know if you have it?A health care provider will test your urine or a specimen (a sample of cells) from your cervix.
How is it treated?Chlamydia can be cured with antibiotics. Any of your sex partners should be treated too in case they caught it (and can give it back to you or someone else). Don’t have sex until your treatment is finished.
Genital herpes 
What is it?

Genital herpes (say: JEN-ih-tul HER-peez) is caused by a virus called herpes simplex virus (HSV). There are 2 types of herpes virus that cause genital herpes: HSV-1 and HSV-2. Usually, genital herpes are HSV-2. But a person with HSV-1 — that’s oral herpes or cold sores around a person’s mouth — can pass the virus to another person's genitals during oral sex.

Genital herpes can increase the risk of HIV infection. That’s because HIV can enter the body more easily where there's a break in the skin, such as a herpes sore.

What are some symptoms?

Some people have no symptoms. Symptoms can include:

  • Small red bumps, blisters, or open sores on the vagina or anus (bottom)
  • Fever, headache, and muscle aches
  • Swollen glands in the genital area
  • Itching or burning in genital area
  • Pain in legs, buttocks, or genital area
  • Pain when urinating

Symptoms may go away and then come back. Sores usually heal after 2 to 4 weeks. If the sores are mild, a person might think they are just bug bites or other skin problem.

How could you get it?Herpes can be spread by vaginal, anal, and oral sex or other sexual contact. It spreads most easily through contact with open sores, but you can get it from skin that doesn’t seem to have a sore too. It also can be passed to a baby during birth, which can be very serious.
How do you know if you have it?Your doctor may be able to see sores and take fluid from them to be sent to a lab for testing. If not, he or she may do a blood test.
How is it treated?There is no cure, but medicine can help make the periods when you have sores shorter and less frequent. Even if you’re taking medicine, you can spread herpes when you have sores, so wait until they’re gone to have sex. (And even if you have no sores, there’s still a chance you can pass along the disease.) Over the years, the times when you have sores usually decrease on their own.
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What is it?Gonorrhea (say: gon-uh-REE-uh) is caused by bacteria that grow easily in the warm, wet environment of your reproductive system. Having gonorrhea can make you more likely to get HIV if you’re exposed to it. Untreated gonorrhea can cause serious problems, including not being able to get pregnant. If untreated, gonorrhea can also spread to the blood, joints, heart, or brain, but this is not common.
What are some symptoms?

Most women have no symptoms or just mild ones. Symptoms can include:

  • Yellowish and sometimes bloody vaginal discharge
  • Pain or burning when urinating
  • Pain during sex
  • Vaginal bleeding between menstrual periods

Gonorrhea infection can also be present in the throat, which may cause a sore throat. It can also be in the anus (bottom). Symptoms there include:

  • Anal discharge
  • Anal itching
  • Soreness
  • Bleeding
  • Painful bowel movements
How could you get it?You can get gonorrhea during vaginal, oral, or anal sex with someone who has it. It also can be passed to a baby when the baby goes through your vagina during birth and can cause serious problems.
How do you know if you have it?Your doctor will do a urine test or take a specimen (a small sample of cells, such as from your vagina) to test.
How is it treated?Gonorrhea can be cured with antibiotics. Any partners need to be treated too, or you can pass the infection back and forth.
Hepatitis B 
What is it?Hepatitis B (say: hep-uh-TY-tis B) is caused by a virus that attacks the liver. It’s also called HBV. If hepatitis B doesn’t go away, it can lead to liver cancer and other serious liver problems. Most babies now get vaccinated for HBV. Talk to your doctor or look at your shot records to see if you were vaccinated. If not, you can still get the shots now to help prevent this serious illness.
What are some symptoms?

You may have no symptoms, or you may have some, including:

  • Yellow skin or yellowing of the whites of the eyes
  • Tiredness
  • Dark-colored urine
  • Stomach pain
  • Loss of appetite
  • Nausea and vomiting
  • Diarrhea
  • Low fever
  • Headache or muscle aches
How could you get it?You can get hepatitis B when an infected person's blood, semen, or other body fluid enters your body. This can happen during sex if you don’t use a condom. It also can happen if you share drug needles with an infected person or if you get a tattoo using a needle with the virus on it. A baby also can get hepatitis B from its mother during birth.
How do you know if you have it?A blood test determines if you have it.
How is it treated?There is no cure for hepatitis B, but it often goes away by itself. Hepatitis B that doesn’t go away may be treated with certain medications. These medications can help slow down the infection, but they are not safe for pregnant women. Sometimes, if a person has been recently exposed to the hepatitis B virus, a doctor will recommend a shot that might prevent the person from coming down with the disease.
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What is it?Human immunodeficiency (say: IH-myoo-noh-di-FISH-uhn-see) virus, or HIV, is the virus that can cause AIDS (acquired immunodeficiency syndrome). HIV and AIDS weaken the body’s ability to fight infections and diseases. Learn more about HIV/AIDS.
What are some symptoms?

Women and girls with HIV may have no symptoms for years. Even if HIV causes no symptoms, it is still causing problems with your body’s immune system that need treatment as early as possible. HIV can lead to AIDS.
Some people have flu-like symptoms within the first few weeks or months after they get infected with HIV.

Symptoms of AIDS include:

  • Weight loss
  • Fevers, chills, and night sweats
  • Being very tired
  • Headache
  • Diarrhea, vomiting, and nausea
  • Mouth, genital, or anal sores
  • Dry cough
  • Rash
  • Swollen lymph nodes
  • Other STIs, vaginal yeast infections, and other vaginal infections
  • Pelvic inflammatory disease (PID) that does not get better with treatment
  • Menstrual cycle changes, like not having periods or having heavy bleeding
  • Human papillomavirus (HPV) infections, which can cause genital warts and cervical cancer

You cannot rely on symptoms to know whether you have HIV. More than half of young people with HIV don’t know they have it. 

You have to get tested to know if you have HIV.

Get tested at least once if:

  • You are 15 or older
  • You are younger than 15 but do things that put you at an increased risk of HIV, such as having unprotected sex or having sex with someone who uses injection drugs
  • You are pregnant

Your doctor may suggest that you get tested more than once if you do things that increase your risk of HIV, such as have unprotected sex or use injection drugs. Find a safe place to get tested.

How could you get it?

You can get infected with HIV when blood, semen (cum), pre-semen (pre-cum), vaginal fluid, anal mucus (fluids in your anus), or breast milk from an infected person enters your body. This can happen during oral, anal, or vaginal sex. It also can happen when these fluids get into an open wound or sore. You also can get HIV from sharing needles for drugs, tattoos, or piercings with an infected person.

Babies can get HIV during pregnancy, birth, and breastfeeding. Treatments can lower the risk during pregnancy and birth, but mothers with HIV should not breastfeed.

You can’t get HIV from casual contact, like sneezing or touching.

How do you know if you have it?HIV tests use blood, oral fluids, or urine. You can ask your doctor or a health clinic about testing. Only two home tests are approved by the FDA: Home Access Express HIV-1 Test System and OraQuick In-Home HIV Test. Be careful: You can buy other HIV home tests online, but they are not approved by the FDA and may give wrong results.
How is it treated?There is no cure for HIV, but there are treatments that help infected people live longer and healthier lives. It’s important to get treatment early.
Human papillomavirus (HPV) 
What is it?

Human papillomavirus (say: pap-uh-LOH-muh-veye-russ), or HPV, is the most common STI in the U.S. Some types of HPV can cause cervical cancer and genital warts. It often goes away on its own.

A vaccine can help prevent the types of human papillomavirus (HPV) that cause most cases of cervical cancer and genital warts. Ask your doctor about getting vaccinated. 

What are some symptoms?

Some women have no symptoms. Symptoms can include:

  • Warts on the genitals or thighs that can be flat or raised and alone or in groups. They may cause itching, burning, or pain.
  • Growths on the cervix and vagina that the person often can’t see
How could you get it?HPV is passed through skin-to-skin contact, like contact between one person’s genitals and the genitals of someone else with HPV. Most often, it’s passed during vaginal or anal sex.
How do you know if you have it?Your doctor may use a magnifying lens to look for warts. He or she may also put vinegar on the genital area so the warts become white and easier to see. A Pap test can find cervical cell changes early, so they can be treated before they turn into cancer. There is also an HPV test that can find HPV on a woman’s cervix.
How is it treated?There is no treatment for HPV, but there are treatments for the conditions that it can cause, like genital warts and cervical cell changes. For example, warts can be removed through special medications or through minor surgery.
Pubic lice 
What is it?Lice (a kind of tiny insect) that feed on human blood. Also known as “crabs.”
What are some symptoms?

Symptoms can include: 

  • Itching in the pubic area
  • Finding lice or eggs
  • Sores from bites or scratching
  • Rust-colored spots on your underwear
  • Mild fever and tiredness if you’ve been bitten by a large number of lice
How could you get it?Usually a person gets it through skin-to-skin contact with someone who already has it. It’s also possible to get it from toilet seats, bedding, and clothing.
How do you know if you have it?You may be able to see the lice yourself, but a doctor can tell you if you have them.
How is it treated?A prescription or over-the-counter medicine can kill the adult lice and egg lice. You should also wash any sheets and clothes that could have lice in them.
What is it?Syphilis (say: SIF-uh-luss) is caused by a bacteria. The sores caused by syphilis make it easier to get or give someone HIV during sex. If syphilis is not treated, it can lead to death.
What are some symptoms?

There may not be any symptoms for years. Different stages have different symptoms.

Symptoms in the first or primary stage appear 10 to 90 days after getting infected. They include:

  • A painless sore, usually in the genital area, but possibly on the lips or other parts of the body
  • Swollen lymph glands

Sores heal on their own. But if the infection is not treated, a secondary stage follows around 3 to 6 weeks after the first sore. Symptoms of that stage include:

  • Rash on the palms and soles of the feet that usually doesn’t itch and goes away on its own
  • Fever
  • Swollen lymph glands and sore throat
  • Patchy hair loss
  • Headaches and muscle aches
  • Weight loss
  • Tiredness

If the infection is still not treated, it moves on to a hidden or latent stage. Then it can possibly enter a tertiary or last stage. During this stage there can be damage to the brain, nerves, eyes, heart, and blood vessels. Some people may even die.

How could you get it?You can get syphilis through direct contact with a syphilis sore. Sores usually are on the genitals, vagina, or anus (bottom). Sores also can be on the lips and in the mouth. That means you can get it during vaginal, anal, or oral sex but also by touching a sore with an open cut you have. A pregnant woman also can pass it to the baby she is carrying, which can be very dangerous.
How do you know if you have it?A health care provider can do a blood test or take a culture (small sample) from a sore to learn if you have syphilis.
How is it treated?If it is treated early, syphilis can be cured with antibiotics.
What is it?Trichomoniasis (say: TRIK-uh-muh-NEYE-uh-suhss) is caused by a parasite (a tiny organism that feeds off you). It is sometimes called “trich.” Trichomoniasis is very common in sexually active young women. Having trichomoniasis increases your chances of getting HIV if you’re exposed to it.
What are some symptoms?

Some women don’t have symptoms, but those who do can have symptoms appear between 5 and 28 days after exposure. Symptoms can include:

  • Frothy, yellow-green vaginal discharge, which has a strong odor
  • Discomfort during sex and when urinating
  • Irritation and itching of the genital area
  • Sometimes, lower abdominal pain
How could you get it?You can get trichomoniasis if semen or vaginal fluids from your partner are passed to your vagina.
How do you know if you have it?Your health care provider will likely give you a pelvic exam and take a sample of your vaginal fluid to test.
How is it treated?Trichomoniasis usually can be cured with antibiotics. Your partner should be treated too. You should not have sex until the treatment is finished and you both have no symptoms.


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Content last reviewed February 02, 2012
Page last updated October 31, 2013

U.S. Department of Health and Human Services, Office on Women's Health.