Sexually transmitted infections (STIs)


Sexually transmitted infections (STIs), commonly called sexually transmitted diseases (STDs), are infections passed from one person to another through sexual contact.

Sexually transmitted infections are very common, especially under the age of 25, because young people are more likely to be sexually active and have unprotected sex. A young girl’s cervix is also more prone to infection by certain STIs.

An estimated 1 in every 4 teenagers and young adults will get a sexually transmitted infection each year.

Girls tend to have more frequent and more serious health problems from these infections than boys.

Patients can be seen by Texas Children's experts in Adolescent Medicine and Pediatric and Adolescent Gynecology.

Causes & Risk Factors

Sexually transmitted infections are caused by having sexual contact with someone who already has an infection, even if that person does not have any symptoms. STIs are passed from person to person through vaginal, oral or anal sex – any contact that involves exposure to infected body fluids such as blood, vaginal fluid or semen. Anal sex is particularly high risk because it typically causes bleeding.

While most STIs are spread through direct sexual contact, they can also be spread through sharing needles or syringes used for drugs, ear piercing or tattooing.

Left untreated, severe sexually transmitted infections can make it more difficult for a young woman to become pregnant in the future. Early diagnosis and treatment can help preserve fertility.

Symptoms & Types

Often sexually transmitted infections do not cause any symptoms.

If symptoms do occur, some of the most common include:

  • Sores or blisters on or around the genital area or in the mouth
  • Pain or burning when urinating
  • Abnormal vaginal discharge
  • Vaginal itching
  • Swollen glands in genital area
  • Pain in or around the vagina
  • Pain in the pelvic area or abdomen (sometimes with fever or chills)
  • Lower back pain
  • Bleeding between periods, or heavy periods
  • Pain during sex
  • Headache and/or muscle aches
  • Pain in legs, buttocks, or genital area
  • Fevers and night sweats
  • Quick weight loss

There are more than 20 different STIs. Some of the most common include:

  • HIV (human immunodeficiency virus) – the virus that causes AIDS
  • Human papillomavirus (HPV) – a common viral infection in teens that can cause genital warts and cervical cancer
  • Herpes
  • Gonorrhea
  • Chlamydia
  • Hepatitis A
  • Hepatitis B
  • Hepatitis C
  • Syphilis
  • Trichomonas

Diagnosis & Tests

There is no one screening test for all STIs.  A doctor can perform and examination and determine what test(s) are needed.  Note a Pap test is not intended to screen for STIs.

Diagnosis starts with a detailed medical history – including a discussion of sexual history and partners – and a thorough physical exam.

Diagnosis may also include:

  • Pelvic exam, to look for signs of infection
  • Blood tests
  • Urine tests
  • Fluid or tissue sample – for examination under a microscope

Early diagnosis and treatment offer the best chance for curing the disease, preventing infertility, and preventing the spread to others. If diagnosed with a sexually transmitted infection, it is important for a woman to tell her partner so he can get tested and treated. Women with a diagnosed sexually transmitted infection should avoid having sex until they have been treated and are no longer infectious.

Treatment & Care

Treatment depends on the individual, the type of STI, and the severity of symptoms.

Treatment strategies may include medications or, for infections that can’t be cured, treatment strategies to relieve the symptoms.

Left untreated, sexually transmitted infections can cause serious health issues, including:

  • Severe pain
  • Infertility
  • Pelvic inflammatory disease
  • Cancer
  • Brain damage
  • Heart disease
  • Miscarriage or birth defects in babies of infected mothers
  • Infection to other parts of the body
  • Organ damage
  • Increased risk of HIV
  • Death 

Living & Managing

Strategies to protect against sexually transmitted infections include:

  • Abstinence – not having sex
  • Limit the number of sexual partners and choose carefully
  • Have partners tested for STIs if they may have one
  • Use latex condoms during sex and a water-based lubricant to keep the condom from breaking
  • Don't inject drugs
  • Avoid alcohol or drugs, since they can increase risky sexual behavior
  • Get all necessary immunizations
  • Have yearly exams with a doctor
  • Keep in mind birth control pills, shots, implants or diaphragms do not protect against STIs.