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Sexually Transmitted Infections (STIs or STDs)

What are sexually transmitted infections (STIs)?

Sexually transmitted infections (STIs) are medical conditions that you get through having sex (vaginal, oral, or anal) or skin-to-skin contact. They are also called sexually transmitted diseases (STDs). 

STIs can be caused by bacteria, viruses, or parasites. Treatment depends on the cause of the infection. Bacterial and parasitic STIs (like chlamydia, gonorrhea, syphilis, and trichomoniasis) are usually curable with antibiotics or other medicines. Viral STIs (like HIV, herpes, and HPV) are usually managed with treatments that control symptoms and reduce transmission to others. 

It’s important to complete treatment and avoid sex until you are cleared by your care team. Make sure your partner gets tested and treated too. 

Talk to your care team about STI screening (testing) and ways to reduce your risk of STIs, including available vaccines. Make sure your sexual partners get tested regularly for STIs too.

Symptoms of STIs

STIs are very common. Some people with STIs have symptoms, while others have no symptoms and may not know they have an STI. 

Common symptoms of STIs can vary depending on the specific infection. Signs and symptoms of STIs may include:

Genital or urinary symptoms

  • Pain or burning during urination (peeing)
  • Frequent urination
  • Unusual vaginal or penile discharge (color, odor, or consistency changes)
  • Genital itching, irritation, or swelling
  • Sores, blisters, warts, or rashes on the genitals or nearby skin
  • Pain during sex

General body symptoms

  • Lower abdominal or pelvic pain
  • Fever or flu-like symptoms
  • Swollen lymph nodes (especially in the groin)

Rectal or oral symptoms  

  • Anal itching, pain, or discharge
  • Sores, blisters, warts, or rashes on the anus, mouth, or nearby skin
  • Sore throat or mouth ulcers after oral sex

It is important to get tested and seek the right care to avoid health problems, as some problems may be serious.

Diagnosis of STIs

If you are sexually active, regular STI testing is important, even if you have no symptoms. Getting tested is quick, private, and often free or low cost. 

Even if you do not think you have an STI, regular screening is a good way to take care of your body and your future health. 

Your care team will do a physical exam to check for visible signs like sores, warts, or rashes. They will ask about your medical history including your symptoms, recent illnesses, and any medicines you take. 

Lab tests for STIs include: 

  • Swab tests: For this test, a sterile swab is used to collect a sample of cells and fluid. Samples may be taken from the genitals, throat, or rectum.
  • Urine tests: Your care team may collect a urine (pee) sample for testing. A urine culture and urinalysis can detect germs or substances that indicate an infection or other health problems. A urine test is often used to check for chlamydia and gonorrhea.
  • Blood tests: Some STI tests involve drawing a blood sample and sending it to the lab for testing. Blood tests can detect infections such as HIV, syphilis, or hepatitis.   
  • Pap test / HPV test: A care provider uses a small brush or swab to collect cells from the cervix to check for changes. This is known as a Pap test, Pap smear, or cervical cytology. 

Ask your care team how often you should get tested. Most health care providers recommend testing for STIs once a year. If you have new or multiple sexual partners, more frequent testing is recommended. Talk to your health care provider for specific STI screening recommendations. 

Treatment of STIs

Treatment for STIs depends on the cause. STIs caused by bacteria and parasites may be treated with antibiotics or antiparasitic medicines. STIs caused by viruses may be managed with antiviral medicines and medicines for symptom relief. 

Vaccines are available for some STIs and can help prevent infection. 

Prompt treatment of STIs is important to reduce the risk of complications and to prevent the spread to others. If left untreated, STIs can lead to serious health problems, such as:

  • Pelvic Inflammatory Disease (PID) 
  • Increased risk of HIV 
  • Increased cancer risk 
  • Organ damage 
  • Chronic pain
  • Problems during pregnancy
  • Spreading the infection to your unborn baby 

With most STIs, you should feel better within a few days to a week after taking the full course of medicine and following your care team’s instructions. After treatment, avoid sexual contact until you are cleared by your care team.  

Be aware that you can get an STI again, even after you have completed STI treatment.

Common Types of STIs

  1. Chlamydia

    Chlamydia is a common STI that often has no symptoms. It can cause serious health problems, especially for women. If not treated, chlamydia can make it harder for a woman to get pregnant or lead to dangerous pregnancies that form outside of the womb (ectopic pregnancy). Even if you have no symptoms, you can still have chlamydia and pass it to others.

    Learn more about chlamydia. 

  2. Gonorrhea

    Gonorrhea is a very common and treatable STI that can affect the genitals, rectum, or throat. It can cause serious health problems if it is not treated. Gonorrhea is often found in young people ages 15–24. Women may notice pain when peeing, vaginal discharge, or bleeding between periods. Men may have pain when peeing, discharge from the penis, or swollen testicles. However, people with gonorrhea often do not have any symptoms. Anyone who is sexually active can get gonorrhea by having sex without a condom with someone who has the infection. 

    Learn more about gonorrhea.

  3. Syphilis

    Syphilis develops in stages, with different signs like sores, rashes, or sometimes no symptoms at all. You might not notice anything for years, but the infection can still harm your body. Syphilis can also be passed from a pregnant person to their baby.

    Learn more about syphilis. 

  4. Bacterial vaginosis (BV)

    Bacterial vaginosis (BV) is a common and treatable vaginal condition, especially in women ages 15–44. Things like douching, not using condoms, or having new or multiple sex partners can change the kinds of bacteria that normally live in the vagina.  This can raise your risk for BV, even if you haven’t had sex. Having BV can also make it easier to get other STIs and cause problems during pregnancy.

    Learn more about BV.

  5. Human Immunodeficiency Virus (HIV)

    HIV is a virus that weakens your immune system, making it harder for your body to fight off infections. There is no cure, but with the right treatment, people with HIV can live long, healthy lives. If not treated, patients with HIV may develop AIDS, a condition where your body can’t protect itself from getting really sick. HIV spreads through blood and other body fluids.  It can also pass from a mother to her baby, during pregnancy or through breastfeeding. Starting treatment early is especially important for young people to stay healthy.

    Learn more about HIV on Together by St. Jude™ and the CDC.

  6. Human Papillomavirus (HPV)

    HPV is a very common virus with many types, and it can infect areas like your mouth, throat, and genitals. Some types cause warts, while others can raise your risk for cancer. Sometimes, there are no symptoms of HPV. Most people get HPV at some point, and your body usually clears it. But sometimes it sticks around, especially if your immune system is weak. If HPV does not go away, it can cause abnormal cells that might turn into cancer if not treated. The HPV vaccine is effective against HPV. 

    Learn more about HPV on Together by St. Jude™ and the CDC. 

  7. Herpes

    Genital herpes is a common STI that anyone who is sexually active can get, and it can be treated. Most people do not notice any symptoms or just have mild symptoms, so many people don’t know they have it. When symptoms do show up, they can include painful blisters or sores around the genitals, rectum, or mouth, and sometimes flu-like symptoms. Genital herpes is a lifelong infection, but outbreaks usually get less frequent and milder over time.

    Learn more about genital herpes and herpes treatment guidelines. 

  8. Hepatitis B

    Hepatitis B is a disease caused by the hepatitis B virus that affects the liver. Infection can be short-term or longer-term. About half of the people with hepatitis B do not have symptoms and do not know they are infected. If symptoms do appear, they usually start about 3 months after being exposed to the virus. People with long-term infection may not have symptoms until many years later. Hepatitis B spreads through contact with infected blood and body fluids. The best way to protect yourself is by getting all the recommended shots in the hepatitis B vaccine series.

    Learn more about hepatitis B on Together by St. Jude™ and the CDC. 

  9. Trichomoniasis

    Trichomoniasis, or "trich," is a very common and treatable STI caused by a tiny parasite. Most people with trichomoniasis do not have any symptoms, so many do not know they are infected. It is more common in women, especially older women. In women, symptoms can include burning, soreness, or unusual vaginal discharge with a fishy smell. Men may have itching, burning, or discharge from the penis. Sex may feel uncomfortable. Without treatment, trichomoniasis can last for months or years.

    Learn more about trichomoniasis.

How STIs spread

Sexually transmitted infections (STIs) spread when germs pass from one person to another, usually during sexual contact. You can get an STI even if you feel healthy or if your partner does not have symptoms. STIs are not just passed through sex—they can spread in other ways, too.

STIs can spread through:

  • Vaginal, oral, or anal sex
  • Skin-to-skin contact with infected areas (like sores or rashes)
  • Sharing sex toys without cleaning them
  • Contact with infected blood, semen, or vaginal fluids
  • Pregnancy, birth, or breastfeeding from mother to baby

How to Prevent STIs 

To help prevent STIs:

  • Get vaccinated against HPV and hepatitis B. 
  • Limit the number of sexual partners or abstain from sex.
  • Make sure both you and your partner get tested for STIs before having sex. 
  • Have regular STI screenings as part of routine wellness exams.
  • Use barrier methods like an external condom (male), internal condom (female), or dental dam each time you have sex.
  • Use a new condom every time you have sex and use it correctly.
  • Communicate openly with your partner. 
  • Limit use of alcohol and drugs.
  • Don’t share needles, razors, or other personal items.
  • Talk to your care team about prevention medicines such as HIV PrEP (pre-exposure prophylaxis) to prevent HIV and doxyPEP (doxycycline post-exposure prophylaxis) to prevent bacterial STIs.
  • Talk to your health care provider about sexual health and safe sex practices. 

Protect Yourself Against STIs

Using condoms and dental dams can lower your risk, but they do not protect against all STIs. Some types of STIs, such as herpes, are spread through skin-to-skin contact.

Birth control pills and some other birth control methods do not protect against STIs.

Regular testing is important to help catch infections early, even if you do not have symptoms.

If you have had unprotected sex with a new partner, are unsure about your partner’s health, or have experienced rape or assault, see a health care provider right away.  

Questions to ask your care team

  • What are STIs, and how do you get them?
  • What signs and symptoms of STIs should I watch for?
  • How often should I get tested for STIs? Should my partner get tested too?
  • Are my STI test results private?
  • How can I avoid getting an STI?
  • How are STIs treated?
  • Do I need to stop having sex while I am being treated for an STI?
  • How do I talk to my partner and my parents about STIs?
  • Will having an STI affect my future health? 

Key points about STIs

  • STIs are infections that spread through sex or other close intimate contact.
  • They are caused by bacteria, viruses, or parasites.
  • STIs are very common and sometimes have no symptoms.
  • Condoms and dental dams lower the risk of STIs but do not give 100% protection.
  • It is important to get regular STI screening, recommended vaccines, and take steps to help prevent the spread of STIs.
  • If you have an STI, stop having sex until you get treatment and are cleared by your care team. Tell your partner and be sure they get tested too.   
  • Talk openly with your care team. They are there to help you and answer any questions. 

Find more information

—
Reviewed: November 2025

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