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Complete Guide to the Most Common Sexually Transmitted Infections (STIs)

Elevation Support 27 April 2026

What are Sexually Transmitted Infections?

How do STIs spread?

How common are STIs?

The Most Common STIs


Chlamydia

Genital Herpes

Gonorrhea

Hepatitis

HIV

HPV

Human papillomavirus (HPV) is one of the two most common STIs in the United States. HPV is so common that almost every person who is sexually active will get HPV at some time in their life. There are many different strains of HPV.

How is it spread? Anyone who is sexually active can get HPV, even if you have had sex with only one person. You can get HPV by having vaginal, anal or oral sex with someone who has the virus.

What are the symptoms? Some types of HPV can cause genital warts and different cancers. Genital warts may appear as a small bump or group of bumps in the genital area. Some people find out they have HPV when their Pap smear has an abnormal result, though they may not have any symptoms.

Can it be cured? No. For most people, HPV goes away on its own and does not cause any health problems. However, if you develop health problems or warts, there are treatments. There is also a vaccine that can prevent the type of HPV that causes cervical cancer.


PID

Pelvic inflammatory disease (PID) is an infection of a woman’s reproductive organs. PID is often caused by some STIs, such chlamydia and gonorrhea. Other infections that are not sexually transmitted can also cause PID. Complications from PID are extremely dangerous to the reproductive system and can lead to ectopic pregnancy or infertility.

How is it spread? PID is not contagious, so you cannot spread it to another sexual partner.

What are the symptoms? Symptoms may be mild to none:

  • Pain in your lower abdomen
  • Fever
  • Unusual vaginal discharge with a bad odor
  • Pain and/or bleeding when you have sex
  • Burning sensation when you urinate
  • Bleeding between periods

Can it be cured? Yes. If diagnosed early, PID can be treated with antibiotics. The longer PID goes untreated, the more likely irreversible complications will develop. Treatment won’t undo any damage that has already happened to your reproductive system. If you have had PID before, your chances of developing it again are higher.


Syphilis

Syphilis is divided into four stages: primary, secondary, latent and tertiary. Each stage has different signs and symptoms.

How is it spread? Syphilis is spread by direct contact with a syphilis sore during vaginal, anal or oral sex, or from an infected mother to her unborn baby.

What are the symptoms? The signs and symptoms of primary and secondary syphilis may be so mild that an infected person might not notice them.

  • Primary syphilis starts when a sore or sores appear where the infection first enters the body. Sores appear on or around the penis, vagina, anus, in the rectum, on the lips or in the mouth. These sores are usually (but not always) firm, round and painless.
  • Secondary syphilis can include a fever, skin rash and swollen lymph nodes.
  • The latent stage has no signs or symptoms and may last for years.
  • Tertiary syphilis is associated with severe medical problems, affecting the heart, brain and other body organs. If untreated, syphilis may extend into the brain and the eye.

Can it be cured? Yes. Syphilis can be cured with specific prescription antibiotics. 


Trichomoniasis

Trichomoniasis, or “trich/trick,” is the most common curable STI. Trich is caused by infection with a parasite called Trichomonas vaginalis. Infection can increase your risk of getting or spreading other STIs, including HIV.

How is it spread? Trich is spread through sex from a penis to a vagina, from a vagina to a penis, or from a vagina to another vagina.

What are the symptoms? Most people infected with trich do not have symptoms. When symptoms are present, they can come and go.

  • Symptoms in men: Itching or irritation inside the penis; burning after urination or ejaculation; discharge from the penis; discomfort having sex.
  • Symptoms in women: Genital itching, burning, redness or soreness of the genitals; urination pain or discomfort; a change in vaginal discharge that can be clear, white, yellowish or greenish with an unusual fishy smell; discomfort having sex.

Can it be cured? Yes, with medication. You can get trich repeatedly though. To avoid reinfection, all sex partners should be treated with antibiotics at the same time. All partners should also wait to have sex again until everyone has been treated and any symptoms go away (usually about a week).

Preventing STIs

The only way to completely protect yourself against STIs is to not have oral, vaginal or anal sex (abstinence). If you decide to have sex, the following actions will help reduce your risk of getting an STI:

  • Talk with your partner about how you both plan to prevent STIs and pregnancy
  • Talk about birth control methods
  • Get vaccinated. Vaccines are available for HPV, hepatitis A and hepatitis B
  • Get tested for STIs before having sex – both you and your partner
  • Learn how to properly use a condom
  • Always use a condom with vaginal, anal or oral sex, from start to finish with a new condom for each sex act
  • Be monogamous – you and your partner only have sexual contact with each other
  • Avoid mixing alcohol and/or drug use with sex, which make people more likely to take risks

Getting Tested for STIs

Girls and young women may have extra needs to protect their reproductive health. Talk to your healthcare provider about regular STI testing, such as cervical cancer screening, and chlamydia and gonorrhea testing.

  • Where do I go to get tested? NJFPL-supported health centers provide affordable and accessible STI testing and treatment. Finding a health center near you is easy. There is at least one in every county of New Jersey, and the services are low or no-cost.
  • What can I expect at a screening? Many people don’t get screened for STIs for fear of the unknown. Will it be embarrassing? Will it be expensive? Will it hurt? The truth is, STI screenings are important and beneficial to anyone who is sexually active. STI screenings are worth the peace of mind alone, not to mention all the health benefits to be gained from early detection and treatment. Remember, doctors, nurses and other healthcare professionals are there to help, not to judge.

If you are experiencing symptoms of an STI or are sexually active and want to get tested, contact your local healthcare provider right away. Find the NJFPL-supported health center that is closest or most convenient to you and call to set up your appointment.