What’s the Difference Between an STI and an STD?

What’s the difference between an STI and an STD? The two terms are often used interchangeably, and while that usage is not always considered to be incorrect, there are some notable differences between the two terms and what they stand for.

STD is by far the more common term. As you probably know, STD is short for sexually transmitted disease, and it is commonly used to refer to infections and diseases transmitted through sexual contact. STI is short for sexually transmitted infection and is also used to refer to infections that are spread through sexual contact. Of the two, STI is the more modern term, though it is less common.

The rise of the STI initialism is due largely to input from the medical community in an effort to impart more clarity in the way that these infectious diseases are discussed and understood. The main reasons for distinguishing between sexually transmitted infections and diseases is that not all infections will lead to a disease and not all sexually transmitted infections have discernible STD symptoms, unlike diseases, which, by definition, must present symptoms. Furthermore, there are sexually transmitted infections that can be cured (or will clear up on their own) without ever resulting in a disease.

HPV virus, both what it looks like by itself and when it has evolved to a cancerous stage.

So, let’s break down that first reason: Not all infections will lead to a disease. Medically speaking, you don’t contract diseases; you contract an infection that could potentially lead to a disease. For example, many people who contract HPV never exhibit any symptoms or develop any conditions related to the infection. In many cases, the infection will go away on its own without treatment. However, in some instances, HPV can develop into types of cancers or lead to the development of warts, in which case the infection would be considered to have progressed to or resulted in the development of a disease.

Another reason a sexually transmitted infection might be classified as an STI instead of an STD is if there are no symptoms present. Medical professionals tend to limit the classification of diseases to those that exhibit symptoms, and many infections that are usually referred to as STDs can be asymptomatic, meaning someone with the infection won’t exhibit any symptoms related to the infection. For example, a person could contract the herpes virus but not display symptoms or have an outbreak for months or even years. While the virus is still asymptomatic, it would be considered an infection. Once the infection begins to develop into outbreaks, it would be considered a disease.

The herpes virus, illustrated, next to an illustration of a stethoscope

Another reason for the push to shift from STD to STI as a descriptor is that, in addition to typically being the more correct term, a sexually transmitted “disease” carries more of a negative connotation than a sexually transmitted “infection.” A disease sounds much scarier, and could prevent people from being comfortable discussing their status. An infection, on the other hand, sounds more unremarkable. While some STD and STIs are incurable and others are curable, the term “disease” doesn’t convey that some of these infections are easily curable with treatment.

So, now you know the difference between an STI and an STD. With any luck, increasing knowledge of these two terms and the nuances in their meaning will lead to better and more transparent conversations about these infections and diseases, which leads to better and safer sex for everyone involved.

An icon of hands, cupped, with a heart floating above them.