Sexually Transmitted Infections (STIs)

Reviewed by: HU Medical Review Board | Last reviewed: April 2024 | Last updated: April 2024

Sexually transmitted infections (STIs), often called sexually transmitted diseases (STDs), are diseases that are passed most often through sexual contact. This includes oral, vaginal, or anal sex. Some doctors prefer to call them STIs instead of STDs because these infections can occur without any symptoms of disease.1

Common STIs include:1

  • Gonorrhea
  • Chlamydia
  • Trichomonas
  • Syphilis
  • Herpes
  • Human immunodeficiency virus (HIV)

How is HIV transmitted?

HIV can be passed from person to person through sexual contact or by contact with blood or other body fluids. Body fluids that transmit HIV include blood, semen, pre-seminal fluid, vaginal fluid, rectal fluid, and breast milk. These fluids must come in contact with open skin or a mucous membrane such as the inside of the mouth, eyes, vagina, penis, or rectum.2

Aside from sex, HIV can be transmitted through needles, unclean tattoo equipment, or a contaminated sharp object.3

Oral sex is much less likely to transmit HIV than vaginal or anal sex. (However, most other STIs can be transmitted through oral sex.) It is also very rare to transmit HIV through food contamination, biting, spitting, or open-mouthed kissing.3

How are STIs related to HIV?

If you get an STI, you are more likely to get HIV. The reverse is also true – if you have HIV, you are more likely to contract another STI. This is because the actions that put you at greater risk for one STI also put you at greater risk for other STIs. The most important risk factor for both HIV and other STIs is having unprotected sex with multiple people.4

Also, STIs like herpes can cause open sores. These breaks in the skin can allow HIV to access your body more easily. And HIV can weaken your immune system, which makes it more difficult for your body to fight off other STIs.4

Symptoms of STIs

STI symptoms can vary between people and between diseases. Common symptoms include:1

  • Burning sensation while urinating (dysuria)
  • Vaginal or penile discharge that may have a strong odor or that is yellow, green, or gray in color
  • Rashes or open sores on the genitals
  • Fever
  • Pelvic pain

STI treatment

STIs can be caused by bacteria, parasites, or viruses. STI treatment focuses on killing off those organisms. The most common treatments include antibiotics and antiviral drugs.1

STIs caused by bacteria and parasites can be cured, but those caused by viruses cannot be cured. Herpes and HIV are examples of STIs caused by viruses. Treatment can still effectively reduce the symptoms and the likelihood of transmitting these viruses to a partner.1

STI prevention

The only guaranteed way to avoid STIs, including HIV, is to not have oral, vaginal, or anal sex. But there are ways to be safer when sexually active. These include:4

  • Getting tested in between partners and ensuring that your partners have been tested
  • Consistent condom use, including changing condoms between every act of vaginal, anal, or oral sex
  • Being aware of how alcohol and drug use may affect your ability to make decisions regarding sex
  • Talking to your doctor to find out if you are a candidate for medicine to prevent HIV

If you believe you have an STI, or if you have more questions about testing and prevention, talk to your doctor.

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Treatment results and side effects can vary from person to person. This treatment information is not meant to replace professional medical advice. Talk to your doctor about what to expect before starting and while taking any treatment.