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Sep 23, 2021
4 min read

STI vs. STD: what’s the difference?

The terms might seem interchangeable, but they are two different things. STIs are sexually transmitted infections, which are similar (but distinct) from sexually transmitted diseases or STDs.

linnea zielinski

Reviewed by Yael Cooperman, MD

Written by Linnea Zielinski

Disclaimer

If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

Although STI and STD are both terms that generally refer to the same set of conditions (including chlamydia, gonorrhea, and herpes) there is a difference.

Sexually transmitted infections (STIs) are transmitted through sexual contact and may be caused by bacteria, viruses, or parasites. A sexually transmitted disease (STD) is when an infection turns into a disease. 

So, if a person is infected and never shows any signs or symptoms of disease (like most people with human papillomavirus or HPV), they are diagnosed with an STI. Someone is diagnosed with an STD once they are actively experiencing symptoms of an infection.

But some of this distinction comes down to stigma. According to the Centers for Disease Control and Prevention (CDC) estimates, approximately 1 in 5 Americans had an STI on any given day in 2018. Unfortunately, despite how common these conditions are, the stigma around them is still very much alive (Kreisel, 2021). 

It’s important to remember that the most common conditions––like chlamydia and gonorrhea––are both treatable and curable with a simple course of antibiotics (Garcia, 2021).

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Infection vs. disease: how to tell the difference

The terms infection and disease have been used interchangeably for long enough that the differences are confusing. 

To boil it down, an infection comes before a disease but doesn’t always cause disease. An infection happens as soon as a parasite, virus, or bacterium enters your body and begins to multiply.

Disease occurs only when the thing that has infected you starts damaging cells. For example, gonorrhea is an STI that can cause pelvic inflammatory disease (PID), if left untreated (Jennings, 2021).

You can be symptomatic (experiencing symptoms) or asymptomatic (not experiencing symptoms) with either an infection or a disease. However, having symptoms doesn’t automatically mean you have a disease. 

When we have an infection, our immune system rushes in to kick out foreign parasites. In most cases, this reaction is a good thing and you may notice symptoms like fever, headache, or rash. But once an infection has progressed to disease, symptoms that appear are specific to that condition––not general signs of the immune system doing its job. 

How long do STIs and STDs last?

How long you have an STI or STD depends on your health, the initial infection type, and what treatment you get. 

For example, some people can clear HPV without medical intervention. How long that takes depends on that individual’s unique immune system. While everyday infections like the common cold often go away on their own, most STDs require some type of intervention. How quickly it works relies on how soon treatment is started.

Do all STIs become STDs?

No, not all STIs become STDs. That said, it’s always a good idea to get treatment if you have symptoms of an STI.

Chlamydia and gonorrhea can both develop into a more serious condition called pelvic inflammatory disease (PID) if left untreated. Getting early treatment for these conditions can stop them from progressing to this point where more severe, and even permanent reproductive damage can occur.

Unlike other STIs, HPV infections can resolve without treatment in some people. But this isn’t always the case. If you’re experiencing any symptoms of an STI, see a healthcare provider for treatment. Getting tested regularly for STIs and STDs can help catch infections before they worsen.

When to get tested

It can be hard to know when to get tested, even if you get an annual physical. One tip that may be helpful is using specific events in your sex life as an indicator. You may want to consider getting tested for an STI or STD if (Lee, 2016):

  • You have new sexual partners
  • You or your partner have had sexual contact with others and haven’t had a test done in 3–6 months
  • You have a sexual partner whose STI status you don’t know
  • You engage in sexual activity with someone you know has an STI or STD

You should also get tested if you notice any physical changes that may point to an infection. Talk to a healthcare professional about STI testing if you experience any of the following (Garcia, 2021):

  • Burning or itching when you pee
  • Bumps or sores on your genitals, upper thighs, or butt
  • Changes in discharge from your penis or vagina
  • Itching, irritation, or pain around genitals
  • Flu-like symptoms, such as fever and aches

How accurate are tests? 

STI tests are highly accurate, meaning false positives rarely happen. 

The most precise test for many STIs is called a nucleic acid amplification test (NAAT). This type of test effectively detects gonorrhea, chlamydia, and trichomoniasis (CDC, 2014; Hobbs, 2013). 

Medical experts don’t recommend herpes tests for people without symptoms unless they know they’ve had sexual contact with someone who has it (Garcia, 2021; Lee, 2016).

In some cases, it’s possible to have a negative urine test but a positive culture test for certain STIs. If a healthcare provider suggests a follow-up test, this may be what they’re checking. Even if you get a negative result from an STD test, still keep an eye out for symptoms and get tested again if you know you’ve been exposed.

If you get a positive test result, don’t panic. Many common STDs (including gonorrhea, syphilis, and chlamydia) are treatable and curable. Those that are not curable––such as genital herpes or warts––are manageable with proper treatment. Always follow a medical professional’s instructions for the best treatment results.

References

  1. Centers for Disease Control and Prevention (CDC). (2014). Recommendations for the laboratory-based detection of Chlamydia trachomatis and Neisseria gonorrhoeae. Recommendations and reports: Morbidity and mortality weekly reports (MMWR), 63(RR-02), 1–19. Retrieved from https://www.cdc.gov/mmwr/preview/mmwrhtml/rr6302a1.htm
  2. Garcia, M. R., & Wray, A. A. (2021). Sexually transmitted infections. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK560808/
  3. Hobbs, M. M., & Seña, A. C. (2013). Modern diagnosis of Trichomonas vaginalis infection. Sexually Transmitted Infections, 89(6), 434-438. doi:10.1136/sextrans-2013-051057. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3787709/
  4. Jennings, L. K., & Krywko, D. M. (2021). Pelvic inflammatory disease. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK499959/.
  5. Kreisel, K. M., Spicknall, I. H., Gargano, J. W., Lewis, F., Lewis, R. M., Markowitz, L. E., et al. (2021). Sexually transmitted infections among us women and men: prevalence and incidence estimates, 2018. Sexually Transmitted Diseases, 48(4), 208–214. doi: 10.1097/OLQ.0000000000001355. Retrieved from https://pubmed.ncbi.nlm.nih.gov/33492089/.
  6. Lee, K. C., Ngo-Metzger, Q., Wolff, T., Chowdhury, J., LeFevre, M. L., & Meyers, D. S. (2016). Sexually Transmitted Infections: Recommendations from the U.S. Preventive Services Task Force. American Family Physician, 94(11), 907–915. Retrieved from https://pubmed.ncbi.nlm.nih.gov/27929270/