Sexually Transmitted Infections

Sexually transmitted diseases (STDs)

Interview between:

  • Andrew Cunningham, MD

  • Jimmy Chen, MD

Sexually transmitted infections (STIs) are infections that are transmitted through sexual contact. This can be through vaginal, oral, or anal contact.

Cases Per Year (US)

20 million STIs occur per year in the US alone. Of the reportable ones, there were 1,708,569 cases of chlamydia, 555,608 cases of gonorrhea, and 30,644 cases of syphilis in 2017.

General Frequency

STIs are very common. There are estimated to be millions of cases per year.


The risk of contraction increases based on the number of sexual partners and engagement in higher risk sexual practices. All STIs are treatable, but their individual health impacts vary.



What are STIs?

Sexually transmitted infections (STIs)–also referred to as sexually transmitted diseases (STDs)–are viral or bacterial infections that are transmitted through sexual activity. This can include oral vaginal or anal sex and, in some cases, close physical contact. They are extremely common, preventable, and treatable. Some are also curable.

Why is it important to get tested for STIs?

We screen for these infections because they sometimes don’t present with symptoms and, if not detected early, they can lead to serious complications, such as pelvic inflammatory disease, chronic pelvic pain, infertility, and cervical cancer. 

While discussing these topics can be sensitive, it’s essential to be honest when answering questions pertaining to sexual practices and history so that your provider can, without judgement, adequately assess risk and order the most appropriate testing.

What’s the difference between an STI and an STD? Is there one?

Generally, these terms are used interchangeably among healthcare providers and researchers. In recent years, the medical community has leaned more toward the use of STI (sexually transmitted infection) rather than use of STD (sexually transmitted disease). This is because the word “disease” implies something that has clear and distinct symptoms, and it’s entirely possible to have an infection without symptoms, as is often the case with STIs.

What are the most common STIs?

  • By far the most common STI is human papillomavirus (HPV), the virus that causes genital warts and cervical cancer. Some researchers estimate that HPV is likely to be contracted by 80% of the population by the age of 45, and CDC data from 2013-2014 estimated that 42% of men and 40% of women had HPV. That said, these numbers are likely to be declining due to the availability of the HPV vaccine. 

  • Trichomoniasis is an extremely common parasitic STI with an estimated 3.7 million cases

  • Gonorrhea and chlamydia are both bacterial. They are often mentioned together because the same tests are used to detect both, and people are sometimes diagnosed with them at the same time. There were 555,608 cases of gonorrhea in 2017. 1.7 million cases of chlamydia were reported for 2017, a 22% rise since 2013. 

  • Herpes simplex virus (HSV-1 and HSV-2) is the virus that causes genital and oral herpes, which both lead to small blisters around the genitals or mouth. Estimates by the CDC indicate that approximately 776,000 people are newly infected with genital herpes yearly. In the United States, it’s estimated that approximately 56% of people between the ages of 14-49 have evidence of HSV-1 and 16% of people between the ages of 14-49 have HSV-2. While HSV-1 is more commonly associated with cold sores and HSV-2 is most often associated with genital herpes, it’s possible to transmit either strain of the virus to the oral or genital area through oral sex. 

  • There were 101,567 new cases of syphilis, which is bacterial, diagnosed in 2017.

  • There were 39,782 new reported cases of human immunodeficiency virus (HIV) for 2017.  At the end of 2016, it was estimated that over 1 million people were living with HIV in the United States. 

  • Other infections that are not considered to be STIs, but can be associated with sexual or close physical contact are bacterial vaginosis, mulloscum contagiosum (a viral infection causing papules on the skin), and scabies (a skin mite that burrows under the skin). Some of the less common STIs include pubic lice, chancroid, lymphogranuloma venereum, and mycoplasma. While not usually categorized as STIs, hepatitis B and hepatitis C, both bloodborne viruses, can be transmitted by sexual activity.









Connect with our physicians

Andrew Cunningham, MD and Jimmy Chen, MD are both members of the Galileo Clinical Team. Connect with one of our physicians about Sexually Transmitted Infections or any of the many other conditions we treat.

Join Today