Diseases and Disorders > STDs/STIs

The Facts About STDs/STIs

Find out how STDs/STIs will affect your sexual health.

A pair of green hands hold a circle with ST? in the center.

Sexually transmitted infections (STIs) are very common in the United States. It’s estimated that more than half the U.S. population will have an STI in their lifetime. The Centers for Disease Control and Prevention (CDC) estimate there are more than 110 million cases among women and men, with 20 million new cases each year.

Thus, it’s important to stay up to date with the facts, learn how to recognize the symptoms and get tested early before they lead to serious health complications.

What are STDs and STIs?

Though the terms STD (sexually transmitted disease) and STI are often used interchangeably, there are important differences between the two.

Yes, it’s true that STDs and STIs are sexually transmitted, contagious and can lead to symptoms that need to be treated medically. And while it’s true to say all STDs start as STIs, not all STIs progress to the point of becoming STDs.

A sexually transmitted infection is just that, an infection and not a disease. Sexually transmitted infections are typically caused by bacteria, viruses or parasites that enter the body through the anus, penis or vagina, which can spread throughout the body, leading to an array of symptoms.

Pubic lice or scabies are not considered to be an STI even though they are spread through sexual contact.

When an STI is left untreated, it can develop into a disease, which we call a sexually transmitted disease. A few STDs that untreated STIs can develop into include:

There are some notable exceptions to this rule, such as human papillomavirus (HPV). It is known to be the most common STI in the U.S., and about 80 percent of women will get at least one type of HPV in their lifetime.

National statistics indicate about 90 percent of women with HPV clear the infection naturally within a couple of years. However, HPV is typically asymptomatic, leaving many who have it unaware of the infection. When a woman isn’t naturally cleared of HPV and has persistent infections, she is at greater risk for developing cervical cancer.

The CDC reports that some of the most prevalent STDs/STIs include chlamydia, gonorrhea, hepatitis, herpes, HPV and HIV (human immunodeficiency virus), which in its later stage becomes AIDS (acquired immunodeficiency syndrome).

Facts, stats and history

The history of STDs and STIs is a long one. These infections and diseases, once referred to broadly as venereal diseases, have been noted throughout history. For example, syphilis first became widely recognized and written about in the 1460s. Additionally, historians believe ancient Chinese and Egyptian people were aware of gonorrhea.

Though more treatments have become available for many STDs and STIs as a result of medical advancement over the centuries, cases of some of these diseases and infections have hit all-time highs in recent years. For example, though syphilis was nearly eliminated a few decades ago and gonorrhea rates were recently at the lowest they’d been, lately there have been significant surges in their prevalence.

Experts believe lack of access to healthcare, inadequate sex education and a lack of resources are all contributing factors to this rise.

Causes and risks

The causes of STDs and STIs include:

  • Bacteria. STDs such as syphilis, gonorrhea and chlamydia fall into this category.
  • Parasites. Trichomoniasis is an STI caused by the parasite Trichomonas vaginalis (TV).
  • Viruses. HPV and genital herpes are caused by viruses. (HIV is a virus.)

Some infections can be considered STIs when they are spread through sexual activity, but people can become infected by them without sexual contact. Examples of these infections would be shigella infection; hepatitis A, B and C viruses; and giardia infection, according to Mayo Clinic.

A number of factors can put an individual at greater risk of contracting an STI or STD. These include:

  • A personal history of STIs
  • Being ages 15 to 24
  • Being forced into sexual activity
  • Having sex with multiple people
  • Injecting drugs
  • Misusing alcohol or recreational drugs
  • Not practicing safer sex

Signs and symptoms

The symptoms of STDs and STIs are wide-ranging. In some cases, symptoms may be obvious—or mistaken for signs of other more common conditions—while in other situations, an STI or STD may be completely asymptomatic.

That being said, some of the most common signs and symptoms that may indicate the presence of an STI or STD include:

  • Burning or pain during urination
  • Fever
  • Painful intercourse
  • Penis discharge
  • Rash on the hands, feet or trunk of the body
  • Small bumps or sores on the genitals, anus or mouth
  • Swollen lymph nodes
  • Unusual bleeding from the vagina
  • Unusual or foul-smelling vaginal discharge

Signs and symptoms may emerge within days after exposure to infection, but it can also take months or years for noticeable symptoms to manifest.

When to call the doctor

If you think you might have been exposed to an infection or you experience any signs or symptoms of a potential STI, make an appointment to see your doctor. It’s also a good idea to ask your doctor for routine STD testing, particularly before you start having sex with someone new.

You might consider inviting the new person you are considering having sex with to get tested with you. It may seem like an embarrassing start to a romantic relationship, but it will benefit all parties' long-term sexual health.

Diagnosis and testing

If you're experiencing symptoms and you have risk factors for an STD or STI, your doctor will likely conduct a pelvic exam to assess any physical signs of infection such as genital warts, abnormal discharge, rash, or bumps and lesions. To confirm a diagnosis, lab work will be done to consider the cause of the infection.

This is the same lab work that is often done on individuals who undergo routine STD/STI testing. This includes blood tests and urine samples. If an individual has open sores, any fluids may be collected for testing.


The appropriate treatment for an STI or STD depends on the cause. For example, when an STD or STI is caused by bacteria, it's typically easier to treat.

Viral infections can be successfully treated with antiviral medications, but they don’t always fully go away and must be managed long-term. This is the case with viruses such as herpes and HIV.

If you are a man who has sex with other men, talk to your doctor about taking preventive drugs such as PrEP (pre-exposure prophylaxis), which reduces your chances of contracting HIV.

If you suspect you may have an STI or STD and you're pregnant, inform your doctor right away. There are treatments available to reduce complications and the risk of passing the infection or disease to your child.

STDs, STIs and infertility

When chlamydia or gonorrhea goes untreated, it can develop into pelvic inflammatory disease (PID) and cause infertility. The CDC reports that about 10 percent to 15 percent of women with chlamydia develop PID.

Untreated chlamydia can lead to an infection of the fallopian tubes that can permanently damage the fallopian tubes, uterus and other nearby tissues, which can cause infertility.

Fortunately, both chlamydia and gonorrhea—both can lead to fertility complications when left untreated—are both preventable and treatable.

CDC recommends that all sexually active women younger than 25 and women at high risk for STIs undergo annual screening for chlamydia and gonorrhea in order to avoid serious complications such as infertility.

STDs and STIs during pregnancy

Pregnant women can contract STIs and STDs. In some cases, a woman may already be infected when she becomes pregnant.

The CDC recommends that pregnant women ask their doctors to test them for STIs/STDs, especially because this is not always a routine procedure for some doctors.

Having an STI or STD can affect your own health as well as the health and development of your baby. Therefore, it’s important to get tested when trying to become pregnant and to continue practicing safe sex throughout your pregnancy.

Chlamydia, gonorrhea, syphilis, trichomoniasis and bacterial vaginosis can be safely treated and cured with antibiotics during pregnancy. However, STIs and STDs caused by viruses, such as genital herpes, HIV or hepatitis B, cannot be cured.

According to the CDC, however, treating these infections with antiviral drugs and other preventive measures may be taken to reduce the chances of passing the infection to the baby.

Prevention and aftercare

Abstinence from all sexual activity is the only surefire way to protect yourself from STDs and STIs. However, this restrictive approach isn’t realistic for most people. Even individuals in a monogamous relationship may not be completely safe, seeing as one or both partners may have an unknown dormant STI such as HPV.

If abstinence doesn't work for you, it’s important to know how STDs and STIs spread and how to protect yourself, and that includes taking measures to avoid STDs/STIs. These measures include getting the HPV vaccine, getting tested regularly and practicing safe sex through the use of condoms and dental dams.

Clinical trials and research

Clinical trials are important tools in the world of medicine that continue to advance scientific research. They often investigate potential cures, treatments and prevention methods for conditions such as STDs and STIs.

If you're considering signing up for a clinical trial, be sure to do plenty of research, and make your final decision in consultation with your doctor and loved ones. A list of active and recruiting clinical trials for various STDs and STIs can be found using this government database.

Resources for patients and caregivers

You can only benefit from learning more about STDs and STIs. Some valuable online resources to get you started on that journey include the following:


How will I know if I’ve caught an STI?

Some STIs show no symptoms at all or take months or years to show signs of an infection. If you have risk factors in your life or you suspect you may have been infected by someone, the only way to know for sure if you have contracted an STI is to get tested. You can make an appointment with your doctor or purchase an at-home testing kit. The results generally take a couple of days.

What is the difference between an STD and an STI?

Both STDs and STIs are sexually transmitted, contagious and can lead to symptoms that need to be treated medically. However, there’s an important difference between the two. STIs are infections—not diseases. If an STI goes untreated, it can progress and develop into a disease. An example would be an untreated STI infection that leads to the development of an STD, such as chlamydia, gonorrhea or syphilis.

What are the most common STDs and STIs?

Some of the most common STDs include chlamydia, gonorrhea or syphilis. The most common STIs include hepatitis, herpes, HPV, Mycoplasma genitalium (Mgen) and trichomoniasis. HIV is a virus that in its latest stage can develop into AIDS.