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STD vs STI: What are the Key Differences?

People often use the terms sexually transmitted diseases and sexually transmitted infections interchangeably, but what they don’t realize is that while these are both illnesses caused by sexual contact, there are some key differences between them. Once you look at the entire term more carefully, you’ll understand that “disease” and “infection” connote two different things. An infection is the invasion of the body by a parasite like a virus or bacteria, in the body whilst disease leads to specific health complications. In this article, we’ll talk about the key differences between STI and STD and the fact that these terms might be used synonymously by some members of the medical community, There is a lot to be said about STD vs STI. 


To distinguish between the two, the most basic things to look at are the terms. STD stands for sexually transmitted disease, and STI stands for sexually transmitted infection. The words disease and infection are what distinguish the two. Sexually transmitted infections are caused by the transmission of bacteria or viruses that first enter the body and then begin multiplying. While sexually transmitted diseases happen after the sexually transmitted disease gets worse and progresses into a disease. 

What does STD stand for?

STD stands for sexually transmitted disease. These were previously referred to as venereal diseases, defining any disease transmitted by sexual intercourse. In the late 20th century the term was supplanted, and such diseases were known as sexually transmitted diseases

What does STI stand for?

STI stands for sexually transmitted infections. This is a synonymous term for sexually transmitted disease although there are some key differences between STI and STD. The word infection distinguishes this term for STD. 

So what is the key difference between STI and STD?

Sexually Transmitted Infections:
Sexually transmitted infections or STIs are referred to as infections that happen after sexual contact that have not progressed into diseases. These infections can be caused by the transmission of microorganisms like viruses, parasites, and bacteria. The transmission happens through sexual activity, after skin-to-skin contact, or the exchange of bodily fluids. Non-sexual activities can also lead to the exchange of such viruses like using the razor blade of someone who has already tested positive for STI. 

Sexually Transmitted Diseases:
On the other hand, sexually transmitted diseases or STDs are diseases that were caused by STIs. These are much more serious in terms of health concerns. All STDs are a result of an STI. Microorganisms enter the body and begin multiplying. When the multiplication of these organisms disrupts and damages normal body function, they become STDs. In some cases, STIs may never develop into STDs. For example, most cases of Human Papillomavirus don’t convert into STDs. But some HPV infections can cause cervical cancer or genital warts. In this case, HPV would be classified as an STD. In last decade, researchers noted that their is a very huge raise in symptoms of std in females which is going up to an alarming situation

Diseases vs. Infections

To understand STD vs STI, we also need to understand the difference between disease and infections. According to some people even these two terms are used interchangeably. But just like STD vs STI, there is a major difference between them. Infection is the invasion of bacteria, viruses, or other microbes in the body that causes minor health concerns. Disease happens when these microbes multiply and start disrupting the normal function of the body. This means an infection has progressed into a disease. An infection basically weakens the immune system, which as a result harms the body and converts the infection into a disease. 

When to get tested?

According to the CDC, if you are a sexually active adult, you need to get tested for STD once a year. If you suspect you are exhibiting any symptoms that may be related to an STD, get tested immediately at your nearest primary care physician. The basic rule is to get tested if:

  • You have multiple sexual partners
  • You have had sex with a new partner
  • You had sex without protection
  • You are worried you got exposed to STI in some nonsexual manner
  • You are pregnant
  • You shared injection with someone

But be mindful about not getting tested too quickly as in that case the test may not be able to detect the infection. 


Sexually transmitted diseases and sexually transmitted infections are becoming a growing health concern in the United States of America. The best way to deal with them is to get tested on time so you can be treated quickly. We offer STD screening services at our facility. Get tested and practice safe sex to protect yourself from such diseases. 


Learn more about STD on Manhattan Medical Arts: Rising In Post Pandemic Std Rates | Std Vs Sti Key Differences | Top 7 Reasons To Get Tested For Stds | Herpes Vaccination Are We There Yet | Gonorrhea The Clap

– Disclaimer –
This blog is for informational & educational purposes only, and does not intend to substitute any professional medical advice or consultation. For any health related concerns, please consult with your physician, or call 911.

Medically Reviewed

Last reviewed by Dr. Syra Hanif, M.D. on 09/06/2021

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  • About The Author

    Dr. Syra Hanif M.D.

    Board Certified Primary Care Physician

Dr. Syra Hanif is a board-certified Primary Care Physician (PCP) dedicated to providing compassionate, patient-centered healthcare.

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