NATURAL HISTORY OF THE DISEASE: PERIODS AND PREVENTION - MEDICINE - 2025

The natural history of the disease refers to the evolutionary process that a pathology undergoes without the intervention of any doctor. In short, it is the course of the disease from its onset to its resolution, but without medical intervention.

When there is a slight or serious alteration of the normal functioning of an organism or of any of its parts, it is said that one is in the presence of a disease. Any disease that manifests itself in humans appears as the result of a dynamic process in which several factors have intervened.

Rembrandt's Dr. Nicolaes Tulp's Anatomy Lesson

The sequence of events that occur in a body, from when the first actions take place until the disease develops and the outcome occurs, is known as the natural history of the disease.

The natural history of the disease used to be widely observed until a century ago when there were not many advances for the treatment of diseases and therefore not for their diagnosis.

Now that science has fortunately provided solutions in the field of medicine, doctors cannot observe this process very easily.

However, without full observation of the natural history of disease in the past, scientists today may not have been able to understand the course of disease.

Therefore, they would not have found a way to detect diseases early to prevent sequelae.

Periods of the natural history of the disease

The natural history of the disease is divided into two periods. The period of genesis, better known as prepatogenic, and the pathogenic period, also called the natural evolution of the disease.

- Prepatogenic period

The prepatogenic period is the phase before the disease. At this stage the disease has not yet developed, which means that the affected person does not present clinical symptoms, or changes at the cellular, tissue or organic level.

But although the body is in balance, it is at this moment when the human being begins to interact with the environment that surrounds it and therefore, it is when the disease process begins.

In this phase, what is known as the ecological triad occurs. This is nothing more than the interaction between three essential components for the development of the disease. These are the host, the agent, and the environment.

Guest

The host is the person or living being that allows the subsistence, housing and development of an infectious agent causing the disease.

This has specific characteristics that must be studied such as age, sex, race, genetic structure, nutritional status, level of immunity, hereditary factors, among others.

Agent

For its part, the agent is any force, principle or living or inanimate substance capable of acting in the organism in a harmful way.

It is who represents the immediate or proximate cause of a disease. Agents can be classified in different ways. But they essentially fall into two groups: biological and non-biological.

• Biological agents: biological agents are bacteria, protozoa, metazoa, viruses, fungi and / or their toxins, among others. They are characterized by being pathogenic, that is, they are capable of producing diseases.

Also for being virulent, since they have a degree of malignancy or toxicity. They also have antigenic power, which means that they have the ability to produce an immune response in the host.

Structure of the influenza virus (flu), a widely spread biological contaminant.

• Non-biological agents: Non-biological agents can be divided into two main ones: chemical and physical. The former involve drugs and toxic substances such as pesticides. The second involve mechanical force, changes in temperature, radiation, electricity, noise, and pressure of gases or liquids.

Non-biological agents can also be nutritional, having to do with poor diets or vitamin deficiencies. And they can also be psychological, involving stress, depression, among others.

Environment

The third component in the ecological triad is the environment. This is the one in charge of promoting the link between the host and the agent.

In this element different factors are involved, which surround an individual. Only factors directly related to the physical environment should not be considered.

When talking about the effect that the environment can have on the course of the disease, there is also an intervention at the interpersonal level, which is the one that includes relationships both as a couple and as a family and close groups of friends, colleagues and even neighbors.

Another factor linked to the environment is related to the social-economic plane. This includes the social structures of the community and the nation, as well as economic development.

In underdeveloped countries there are high levels of poverty, which lead to poor hygiene. Source: pixabay.com

Finally, cultural-ideological factors must be considered. In this case the structure of beliefs and knowledge of the community or society can also affect the individual.

- Pathogenic period

The pathogenic period is the one that occurs when all the circumstances and characteristics of the prepatogenic period coincide in a host.

If this is the case, then the balance of the ecological triad is broken and it is at that moment when the host is affected by the disease. In this stage, cellular and tissue changes begin to occur.

Depending on the type of infection, these changes can occur rapidly as a consequence of the multiplication of microorganisms, their virulence and their ability to produce toxins.

However, in the case of chronic degenerative and mental diseases, for example, this process can drag on for months and even years until signs and symptoms of the disease finally occur.

The pathogenic period is divided into two stages. These are the subclinical period, also known as the incubation or latency period, and the clinical period.

- Subclinical period

The sensation of cold or fever is an indicator that a pathogen may be incubating.

It is the phase in which a causal agent invades the host. This stage is characterized by the appearance of anatomical or functional lesions, although without the presence of signs or symptoms of the disease.

It is then the time that elapses between the moment of stimulation of the disease until the moment when it becomes evident.

In communicable diseases this phase is known as the incubation period and in chronic diseases (physical or mental) it is known as the latency period.

- Clinical period

This phase begins with the first symptom or sign of the disease. This moment is called the clinical horizon. With this first manifestation comes a series of symptoms or signs, as well as complications and sequelae.

When it comes to complications, it is when the disease involves other conditions in the body that can be heart failure, kidney failure or respiratory failure.

Person coughing with breathing problems.

With regard to the sequelae, it is the stage in which people usually present some type of disability or permanent alteration in the body.

As a consequence of the disease, other elements that are part of this stage also appear, such as damage, disability, recovery, chronicity and death.

Death is not necessarily imminent and in any of the phases prior to this, the body can regain balance, that is, health.

Throughout these manifestations, three stages of the clinical period can be distinguished. The first of these is the prodromal period.

This is about the presence of general manifestations of the disease. In this case, the symptoms and signs are often confusing, making it difficult to make an exact diagnosis.

Next is the clinical period itself. This is the time when the disease manifests itself by specific signs symptoms. And in this way its diagnosis and management is easier.

Finally, the resolution period is the final stage. In this phase the disease has three paths: it disappears, it becomes chronic or the patient dies. In the latter case, both brain and cardiac death must occur.

Example of a clinical period of a disease that finally disappears.

Prevention levels

Other elements that affect the natural evolutionary course of the disease may be involved in the development of the disease. With prevention it is possible to interrupt the chain of events that make up the natural history of the disease, which lead to the progressive deterioration of the health of the affected individual.

Diseases can be caused by multiple risk factors. For this reason it is not possible to control them, much less solve them by addressing them from a particular discipline. For this reason it is necessary to place protection barriers, which are called levels of prevention.

When we talk about prevention we talk about anticipation in order to reduce the chances of an eventuality occurring. And that if so, the advance of this can be solved or avoided.

Prevention can only be done based on knowledge of the natural history of the disease, since in this case the goal will always be to reduce the probability that the disease will progress.

There are three levels of prevention: primary level of prevention, secondary level of prevention and tertiary level of prevention.

- Primary prevention level

This first level of prevention is applied during the period of genesis of the disease. That is, during the prepatogenic period.

In this case, the objective is to try to eliminate or reduce the risk factors present in the community. At this level of prevention, the aim is to maintain the health of the individual and promote it through different actions.

To prevent disease and promote health, economic, educational, and social measures are often applied. These include activities related to nutrition, hygiene education, personality development, periodic examinations, water sanitation, garbage, food, noise and everything that has to do with the environment.

Washing your hands properly would help reduce many illnesses caused by viruses, bacteria, and other pathogens.

Among the specific prevention measures that are applied are immunizations, protection against accidents, attention to personal hygiene, elimination of infectious sources, among many other things.

However, despite the fact that all these activities are part of the so-called primary prevention level, it is important to emphasize that prevention and health promotion are not equal actions.

While prevention aims to prevent the disease from deteriorating the individual's state of health, promotion is responsible for facilitating the maintenance of a person's state, increasing their health and well-being.

- Secondary prevention level

This type of prevention is what is applied when primary prevention has failed and therefore the individual becomes ill. This level includes measures that are applied in the latency period of the disease.

At this level of prevention, the objective is to make an early diagnosis that can give rise to subsequent timely treatment.

Computed tomography helps determine the progress of certain conditions such as tumors.

When secondary prevention is applied, it is because it is no longer possible to apply actions that prevent the appearance of diseases. This barrier focuses on making an early diagnosis preferably before clinical manifestations occur.

It also focuses on healing the sick before irreversible damage can occur. Or even in the prevention of complications and sequelae, among other things.

During this level of prevention, therapeutic actions are also carried out in order to reduce the consequences of a disease. These actions can be physical, surgical, dietary, medicinal or psychotherapeutic.

Once a disease has manifested, a good diagnosis that is also timely and is accompanied by appropriate treatment are the best preventive measures that can be applied to prevent the disease from progressing.

- Tertiary prevention level

This is the level of prevention that is applied when it is no longer possible to apply the two previous levels. These are measures that are applied during the period of expression of the disease.

That is, in its symptomatic phase. In this case, an acute and rehabilitative treatment is carried out. It can focus on a rehabilitation process that includes physical, socioeconomic and psychological elements.

The objective is to try to recover the sick individual as far as possible, taking into account the capacities that remain.

Medicines to fight diseases.

Among the measures that can be applied at this level of prevention are the maximum recovery of functionality, the psychosocial change of the patient, occupational therapy, the use of capacities to the maximum, the education of family members, school groups and even companies to disseminate the support of the disabled, among other things.

References

1. Urquijo, L. (no date). Natural history of disease.
2. Donis, X. (undated). Compilation and illustration for educational purposes. Natural history of disease. University of San Carlos of Guatemala. Recovered from saludpublica1.files.wordpress.com.
3. Morales, A. (no date). Natural history of the disease and levels of prevention. Recovered from academia.edu.