STI vs STD: Do They Mean the Same Thing? Here's How Experts Explain It


STI vs STD: Which do you say? You probably heard both terms in health class and have seen both used online in the years since. "STI" stands for sexually transmitted infection, and "STD" stands for sexually transmitted disease. But which one is the correct term when talking about all the different sexually transmitted conditions?

STI vs STD: Which term should you use?

It's totally fine to use the terms interchangeably, H. Hunter Handsfield, MD, professor emeritus of medicine at the Center for AIDS and STD at the University of Washington, tells Health. "In day-to-day uses of the term, there is no real difference," he says.

There's no distinct consensus among the major organizations, either. For instance, the American College of Obstetricians and Gynecologists (ACOG) appears to be more likely to use the term STI. The Centers for Disease Control and Prevention (CDC) uses STD and STI interchangeably, noting that STDs are also known as STIs.

No matter which term you use, the diseases/infections, such as chlamydia, gonorrhea, and syphilis, are passed through vaginal, anal, and oral sexual activity—and they are conditions that 1 in 5 people in the US have, according to the CDC.

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‘Disease’ vs ‘Infection’

While people might be able to use the terms interchangeably in day-to-day convos, there actually are differences between the terms "disease" and "infection."

Technically, a disease is considered an advanced form of an infection, Damian "Pat" Alagia, MD, ob-gyn and the senior medical director for advanced diagnostics and women's health at Quest Diagnostics, tells Health. For example, "if a chlamydia or gonorrhea infection takes off and is untreated or improperly treated, it can progress into pelvic inflammatory disease (PID), which is a complication of the STI that can threaten fertility," Dr. Alagia says. "A disease is a full-blown expression of the underlying infection."

"STI" is a term that "largely evolved from the realization of asymptomatic infections," Dr. Hansfield explains. In other words, bacteria or viruses can cause an infection, but that infection might not have any outward signs or symptoms. Sometimes, the infection—like the human papillomavirus (HPV)—is cleared by the body and goes away on its own. In these cases, the virus did not cause disease.

But that doesn't mean the infection is any less important—or that it should be ignored. There are many instances when you want to respond to an infection even if there are no symptoms because it can still cause disease, Dr. Handsfield says. That's why chlamydia and gonorrhea—both largely asymptomatic infections—are treated with antibiotics if diagnosed. It's also one of the reasons why experts encourage women to get HPV screening and/or pap tests at the appropriate interval for their age. The idea is that certain HPV infections, which are usually asymptomatic, can cause cervical cancer. Knowing if you are infected with high-risk HPV will help your doctor determine any necessary follow-up testing or treat any precancerous lesions to prevent them from progressing into cancer.

Though there is technically a difference between "disease" and "infection," whether you use "STD" or "STI" doesn't matter; it shouldn't change testing, treatment, or other steps you take to safeguard yourself and your sexual partners, Dr. Alagia says. STI or STD, you'll still want to use the same measures to protect yourself and partners, such as having an open discussion about sexual history, using condoms, and getting tested for STIs regularly.

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Which term do health care experts use?

Your doctor may use one or the other depending on their age, training, or preference, according to Dr. Handsfield. It may also have to do with the patient population they see most, a commentary in the journal Sexually Transmitted Diseases suggests. If they're doing a lot of screening in their practice, they may use STI. But if they're treating symptomatic infections or diseases, then they may use STD.

While it's not wrong to use STD, the needle is moving slightly toward using STI, Dr. Handsfield notes. That change might destigmatize these sexually transmitted conditions. As Dr. Handsfield wrote in a 2017 editorial, there is some limited research that suggests there may be less of a stigma surrounding STI.

The switch from STD to STI gets away from the word "disease," according to the American Sexual Health Association (ASHA): "The concept of 'disease,' as in STD, suggests a clear medical problem, usually some obvious signs or symptoms. But many common STDs have no signs or symptoms in most of the people who have them. Or they have mild signs and symptoms that can be easily overlooked," ASHA notes.

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Bottom line

The term you use is up to you. "The important take-home message is that you can use either STI or STD, depending on your preference. But don't pay any less attention to the health impacts of either one," Dr. Handsfiled says. Prevention, diagnosis, and treatment are all important.

Talk to your doctor about the screening tests you need based on your age and sexual history. You should also feel secure enough to ask for a test if you think you need one, adds Dr. Alagia. "When you catch infections early, it will make a big difference in your overall health and well-being," he says.

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