Sexually Transmitted Infections (STIs): What You Need to Know

STI trends during the COVID-19 pandemic are complex and difficult to interpret, according to a new report issued by the CDC this April, but one thing is clear: STI case numbers are still unacceptably high. In 2020 alone, 2.4 million new cases were reported, calling for a stronger public health response to address STIs across the country.

STIs may not be as common as the common cold, but millions of people in the U.S. come down with one each year. Fortunately, most STIs are either curable or manageable with treatment, says Dr. Neil Lim, a primary care physician at Weill Cornell Medicine.  

 If you are confused about the difference between an STI (sexually transmitted infection) and an STD (sexually transmitted disease), let’s clear that up right now. Although the two terms are often used interchangeably, they are not synonymous. An infection does not necessarily cause full-blown disease. In fact, two of the most common STIs, syphilis and gonorrhea, do not even cause noticeable symptoms, and both can be cured way before they turn into a real STD. For this reason, most experts have switched from using STD to the more accurate STI. 

The most common STIs 

Three of the six most common STIs in the U.S. are caused by bacteria:  

  • Chlamydia 
  • Syphilis 
  • Gonorrhea 

These three can be completely cured with a course of antibiotics. 

And the other three are caused by viruses: 

  • HPV (human papillomavirus) 
  • Herpes (herpesvirus) 
  • HIV (human immunodeficiency virus) 

Viral STIs are not technically curable, but effective treatments are available for all three of the common ones listed above, helping to keep symptoms at bay and even prevent transmission. 

Who’s at risk?  

Virtually anyone who is or has ever been sexually active is at risk for contracting an STI. But some people are at higher risk than others, including the following groups: 

  • Anyone who has had unprotected vaginal, oral or anal sex with a new partner 
  • Anyone who has multiple concurrent partners or has a sexual partner who has multiple partners 
  • People between 15 and 24 years old 
  • Men who have sex with men (MSM) 
  • People who have had an earlier STI or who have HIV 
  • People who use illicit drugs 

“Barring abstinence,” says Dr. Lim, “the only way to reliably protect yourself from STI transmission is the consistent use of condoms.” 

How are STIs transmitted?  

The answer to that question may seem obvious—through direct sexual contact, whether vaginal, oral or anal. But there are less direct ways to contract an STI such as: 

  • Sharing unwashed sex toys 
  • Skin-on-skin contact via a sore or wart 
  • Sharing razors, toothbrushes or needles... 
  • ...and, in the case of herpes, kissing. 

Still, sex—the genuine item—is responsible for the majority of STIs. 

 And the only way to find out if you have contracted one is to get tested. 

When should you get tested? 

Be on the lookout for any of the following symptoms and make an appointment to get tested if you notice one or more of them, especially if you have engaged in sexual activity with a new partner: 

  • bumps, warts, sores, or a rash in or around the genitals, anus, buttocks or thighs 
  • any change in the color, smell or amount of vaginal discharge 
  • penile discharge 
  • unusual vaginal bleeding between periods or after sex 
  • rectal bleeding 
  • painful or burning urination 
  • pelvic pain (in women) 
  • painful or swollen testicles 
  • swollen, painful lymph nodes in the groin or neck 

 However, the appearance of symptoms is not the only reason for getting tested. STIs do not always cause obvious symptoms. It is advisable, then, to get tested if you are a member of any of the groups on the “at risk” list.  

There is actually no set age at which STI screening should begin, says Dr. Lim. Women under 25 and men who have sex with men should start getting tested when they become sexually active, and both groups should be screened for STIs at least every year after that.  

Dr. Lim points to three additional groups who should seek annual testing: women over 25 with risk factors, including new or multiple sex partners, a recent history of an STI or participation in transactional sex; men who have sex with men; and anyone with HIV infection. 

But what about exclusively heterosexual men? Members of that group do not require annual screening, says Dr. Lim, “unless they have certain risk factors, such as a history of incarceration, a prior STI or transactional sex work.” 

And finally, the CDC recommends that everyone between the ages of 13 and 64 get tested for HIV at least once in their lifetime.   And remember, anyone with a potential STI exposure can also always request testing from their doctor at any time.

More about Testing 

Early detection is the best way to prevent an STI from becoming an STD down the road. A true STD may have long-term consequences for your health such as infertility or certain cancers.   

But there’s no need to get screened the morning after having sex with a new partner. Wait at least a few days to get tested for chlamydia and gonorrhea, both of which have short incubation periods. By contrast, other infections like syphilis and HIV can take weeks to incubate to the point of eliciting an immune response from the body in the form of antibodies. That’s why it can sometimes make sense to wait about one month before testing to ensure the most accurate results. 

To schedule an in-person or video visit with a primary care provider at Weill Cornell Medicine and  arrange for STI testing, go to or call (646) 962-8000.