STI vs STD vs Sexually Transmitted Virus

Question

I am very confused as in my answer to Why is HIV singled out from other STIs? I agreed with the OP that HIV is an STI.

I have been led to believe the following definitions:

STI

Stands for Sexually Transmitted Infection — an infection caused by bacteria or virus which has been transmitted through sexual contact.

STD

Stands for Sexually Transmitted Disease — a disease caused by the infection of a bacteria or virus transmitted through sexual contact.

With regard to HIV

These definitions class HIV as an infection. This is a fact to me because:

(bold emphasis mine)

Over time, HIV can destroy so many of these cells that the body can’t fight off [other] infections and disease. These opportunistic infections or cancers take advantage of a very weak immune system and signal that the person has AIDS, the last stage of HIV infection (HIV.gov, 2017)<sup>*

* Website managed by the U.S. Department of Health & Human Services and supported by the
Secretary’s Minority AIDS Initiative Fund (SMAIF)</sup>.

HIV is a retrovirus, which is:

a family of viruses that are grouped together based on how they are structured and how they replicate within a host. Besides human immunodeficiency virus (HIV), the virus that causes AIDS, there a two other retroviruses that can cause human illness. One is called human T-lymphotropic virus type 1 (HTLV-1) and the other is called human T-lymphotropic virus type 2 (HTLV-II) (Minnesota Department of Health, n.d.).

Human T-cell lymphotropic virus type 1 (HTLV-1) is primarily transmitted through sexual intercourse or from mother to child (Paiva & Casseb, 2014) making HTLV-1 an STI in definitions I have been led to believe, and AIDS is an STD due to the fact that it is caused by HIV infection which in many circumstances is transmitted through sexual contact, although HIV can be transmitted through other means (see my answer). It cannot be an STI as AIDS is not transmitted. It is a disease as a result of HIV infection.

What creates a confusion?

In the comments to my answer, @Jan stated that HIV is not an STI, but just a virus. To make matters worse, when trying to confirm or deny his responses I have been trying to look up a definitive definition and found that in the key points of this factsheet, it states that:

HIV is an STD. Chlamydia, gonorrhea, human papillomavirus (HPV) infection, and syphilis are examples of other STDs. (National Institutes of Health, n.d.)

So the question is: What is the difference between STIs, STD and "just a virus transmitted through sexual contact"?

References

HIV.gov (2017) What Are HIV and AIDS?
Retrievable from: https://www.hiv.gov/hiv-basics/overview/about-hiv-and-aids/what-are-hiv-and-aids

Minnesota Department of Health, (n.d.) Other Retroviruses That May Cause Human Illness
Retrievable from: http://www.health.state.mn.us/divs/idepc/diseases/retrovirus/index.html

National Inststutes of Health (n.d.) HIV and Sexually Transmitted Diseases
Retreivable from: https://aidsinfo.nih.gov/understanding-hiv-aids/fact-sheets/26/98/hiv-and-sexually-transmitted-diseases--stds-

Paiva, A., & Casseb, J. (2014). Sexual transmission of human T-cell lymphotropic virus type 1. Revista da Sociedade Brasileira de Medicina Tropical, 47(3), 265-274.
DOI: 10.1590/0037-8682-0232-2013 PMID: 25075475

Answer 1

Short Answer

HIV is a virus and when the HIV virus has invaded the body it becomes an infection (specifically an STI only if and when transmitted through sexual contact).

Whilst the terms STI and STD are often used interchangeably, really and truthfully, they are different.

A sexually transmitted virus is an STI when inside the body, and an STI is not necessarily an STD.

Longer Answer

As an example of the confusion which can occur, there are articles that labeled herpes as a “sexually transmitted disease” (STD), while others favoured the term “sexually transmitted infection” (STI) (Depasse, 2017). Even government health agencies like the National Institutes of Health (NIH) use the terms interchangeably (NIH, 2017), often without explanation for doing so. With such ambiguity, it’s hard to discern fact from fiction.

Key Terms

Pathogen: A pathogen is a microorganism that can cause disease. There are five major types of pathogens: bacteria, viruses, fungi, protozoa, and helminths (NIH, 2007).

Infection: An infection resulting from when a pathogen invades and begins growing within a host (e.g., a human) (NIH, 2007; MedlinePlus, n.d.).

Disease: A disease results only if and when, as a consequence of the invasion and growth of a pathogen, tissue function is impaired (NIH, 2007) it is when the body’s ability to perform normal functions is interrupted or changed, usually presenting with certain signs and symptoms. MedlinePlus, n.d.(a)).

With these terms, the definitions of STI and STD in my question stands:

STI

Stands for Sexually Transmitted Infection — an infection caused by bacteria or virus which has been transmitted through sexual contact.

STD

Stands for Sexually Transmitted Disease — a disease caused by the infection of a bacteria or virus transmitted through sexual contact.

Therefore, both Jan and I are correct with regard to HIV. HIV is a virus (a pathogen), and when the HIV virus has invaded the body it becomes an infection (specifically an STI only if and when transmitted through sexual contact). HIV by itself is not a disease (STD) but causes AIDS which is the STD (the symptom of advanced HIV infection). HIV is still present as an STI with AIDS being an STD.

Whilst the terms STI and STD are often used interchangeably, really and truthfully, they are different.

References

Depasse, E. (2017). STD vs. STI: Is There a Difference? And Why Does It Matter? - HealthCentral
Retreivable from: https://www.healthcentral.com/article/std-vs-sti-is-there-a-difference

MedlinePlus. (n.d.). Infection - Medical Dictionary
Retreivable from: https://c.merriam-webster.com/medlineplus/infection

MedlinePlus. (n.d.(a)) Disease - Medical Dictionary
Retrievable from: https://c.merriam-webster.com/medlineplus/disease

NIH. (2007). Understanding emerging and re-emerging infectious diseases. Biological sciences curriculum study. NIH Curriculum Supplement Series. National Institutes of Health, Bethesda, MD.
NIH Bookshelf ID: NBK20370

NIH. (2017). What are some types of and treatments for sexually transmitted diseases (STDs) or sexually transmitted infections (STIs)?
Retreivable from: https://www.nichd.nih.gov/health/topics/stds/conditioninfo/types

Answer 2

STI = sexually transmitted infection

STD = sexually transmitted disease

Strictly speaking, not all STIs are STDs. Infection merely means the presence of the microbes in the body and if it does not cause any symptoms, it is called asymptomatic infection, not a disease. Only when a HIV infection causes damage to the body, which usually comes with symptoms, it becomes a disease (STD), namely AIDS.

HIV = human immunodeficiency virus. When someone catches HIV, he/she only catches a virus, which may or may not cause AIDS. The same way as you can catch some rhinoviruses and as a result you may or may not develop common cold.

MedicalNewsToday: HIV vs. AIDS: What is the difference?

HIV infection and AIDS are not the same condition, and they are not the same diagnosis.

HIV is a virus that attacks a type of white blood cell called a CD4 cell in the body's immune system.

AIDS is a syndrome, or range of symptoms, that may develop in time in a person with HIV who does not receive treatment. A person can have HIV without developing AIDS, but it is not possible to have AIDS without first having HIV.

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Bottom line: HIV = an STI (infection), which may or may not become an STD (disease), called AIDS.