It is important that before entering fully into the meaning of the term etiologic agent, we proceed to know the etymological origin of the two words that shape it:
-Agent is a word that derives from Latin, specifically, from "agentis" that can be translated as "the one who takes the action." It is the result of the sum of two distinct parts: the verb "agere", which is equivalent to "acting", 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 composed of three distinct 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 that which has the ability to produce something or to act . Etiological , meanwhile, is what is linked to the etiology : the analysis of Causes or of the origins of things or diseases.
With these ideas clear, we can move forward in the definition of Etiological agent . It is the element that promotes development of a disease . Bacteria and viruses are among the most common etiological agents.
Take the case of the Rage . This is a viral and contagious disease that attacks the Central Nervous System (SNC ). Once the animal or the person contracts rabies, they begin to suffer various disorders, such as paralysis, hyperactivity and aggressive tendencies, until they enter a coma and, generally, die due to cardiac arrest or due to 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 rabies virus is the etiologic agent that causes this contagious and generally fatal disease.
Saying virus He is the etiological agent since he drives the development of the disease. In other words: without infection of the organism by the rabies virus, the emergence 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 goes for other viruses that cause other disorders.
Another example would be the pathology called Hemolytic Uremic Syndrome (HUS), which may be caused by a wide variety of infectious, etiologic agent conditions, such as Shigella dysenteriae type1, Salmonella typhi, Streptococcus pneumoniae or Campylobacter jejuni.
In meningitis, on the other hand, the most frequent etiologic 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 that type is considered to be the cause of AIDS. We are referring to the Human Immunodeficiency Virus (HIV), which is part of the family of retroviruses and can be of two types: HIV 1 and HIV 2.