Etiological agent

It is important that before entering fully into the meaning of the term etiological agent, we proceed to know the etymological origin of the two words that give it shape:
-Agent is a word that derives from Latin, specifically, from “agentis” which can be translated as “the one who carries out the action”. It is the result of the sum of two differentiated parts: the verb “agere”, which is equivalent to “act”, and the suffix “-nte”, which is used to indicate the person responsible for the action.
-Etiological, on the other hand, comes from the Greek, exactly from the term "aitology", which is made up of three different parts: the noun "aitia", which means "cause"; the noun "logos", which can be translated as "study"; and the suffix "-ia", which is used to indicate "quality".

The concept of agent refers to that or the one who has the ability to produce something or to act. Etiological, for its part, is what is linked to etiology: the analysis of Causes or the origins of things or diseases.

With these ideas clear, we can move forward in defining Etiological agent. It is the element that promotes development of a disease. Bacteria and viruses are among the most common etiologic agents.

Take the case of Rage. This is a viral and contagious disease that attacks the Central Nervous System (CNS). Once the animal or person contracts rabies, they begin to suffer from various disorders, such as paralysis, hyperactivity and aggressive tendencies, until they enter a coma and usually die of cardiorespiratory arrest or infection derived from the general picture. The cause of this disease is a virus, known simply as the rabies virus. It can be said, therefore, that the rabies virus is the etiological agent that causes this contagious and generally fatal disease.

Saying virus it is the etiological agent since it drives the development of the disease. In other words: without the infection of the organism by the rabies virus, the outbreak of rabies is not possible. That is why this virus is defined as an etiological agent, because it is the origin or cause of the disease. The same is true for other viruses that cause other disorders.

Another example would be the pathology called Hemolytic Uremic Syndrome (HUS), which can be caused by a wide variety of infectious conditions, of etiological agents, such as Shigella dysenteriae type 1, Salmonella typhi, Streptococcus pneumoniae or Campylobacter jejuni.

In meningitis, on the other hand, the most frequent etiological agents are gram-negative bacteria, S Pneumoniae or Listeria monocytogenes, for example.

Of course, it should not be overlooked that one of the best-known agents of this type is the one believed to cause AIDS. We are referring to the Human Immunodeficiency Virus (HIV), which is part of the family of retroviruses and which can be of two types: HIV 1 and HIV 2.