What's The Difference Between An STD & An STI?

When I was in school, we learned about STDs (sexually transmitted diseases) in health class. (Who could forget those terrible lists of symptoms and gross images they used to try to scare us, right?) But as I got older, I started hearing the term STI — which stands for “sexually transmitted infection” — more frequently. While the names are clearly different, I couldn’t really tell why there were suddenly two different terms. Were they just two names for the same thing? What’s the difference between an STI and an STD, anyway?

"STI is a more modern and updated term that is replacing STDs," Dr. Gil Weiss, Assistant Professor of Clinical Medicine at Northwestern Memorial Hospital and partner at Association for Women's Health Care tells Bustle. "The term STI reflects that fact that some people who get infected do not experience symptoms or even develop the disease. Most people who get infected by HPV do not develop cervical cancer. Thus infections is a more accurate term than disease."

The CDC tells Bustle that while STI and STD are basically the same thing — and in common usage, they’re used almost interchangeably — but that there are slight technical differences between the two terms. The short version is that STI is a broader term that includes STDs, but not all STIs are STDs. For the longer version, bear with me as I explain, because the differences are pretty subtle.

STIs are infections , and an infection occurs when a parasite enters your body and starts spreading. So, for example, say you have sex with someone who has the HPV virus and they spread that virus to you. You now have an STI, but you might not show any symptoms because HPV often hangs out without presenting any symptoms.

STDs are diseases. Basically, if your STI results in noticeable, uncomfortable symptoms, then it becomes an STD. In the case of an HPV infection, it becomes an STD when you have symptoms such as warts or cervical cancer. But if you never show symptoms? HPV is technically an STI.

This isn’t the first time we’ve changed the name of sexually transmitted illnesses: the term STD started gaining traction in the late 1970s and up until the 1990s, the term “venereal disease” was the name of choice for both medical professionals and the common public. STI was officially adopted by the World Health Organization as the preferred term in 1999, partially because of the slight difference between an infection and disease and also because they — along with other medical professionals — felt that the word “disease” carried too much stigma.

Which is legit — “disease” definitely sounds scarier than “infection” and it is the term they used to scare us back in school — but let’s get back to common usage, shall we? I'd like to make a quick note about the fact that I know how confusing this is — the same illness in the same person can be either an "infection" or a "disease" at different stages. With that in mind, sexologist and relationships expert Dr. Logan Levkoff tells Bustle that IRL, the two terms are basically interchangeable.

“The reason we use STI now is because of the stigma factor,” she tells Bustle. “There may indeed be differences between what an infection is and what a disease is however, no one is going to not call HPV an STD simply because it may not lead to cancer.”

So there you have it! If you want to use the terms STI and STD interchangeably, go for it! But if you want to be technical about it, STIs are the infections and STDs are when your body starts to act in funky ways as a result of those infections. Either way, though, I have one question for you: When's the last time you got tested?

Images: Andrew Zaeh for Bustle; Giphy