Epidemiology: what it is and how it studies diseases

For a few weeks, a certain virus that many of us thought was not going to be that bad has ended up giving us a "pleasant" surprise by inviting us to stay at home. Not out of laziness or because it hasn't been a good day, but because it turns out that the street is, right now, potentially contagious.

Given how alarming the situation we find ourselves in, it is not surprising that people are wondering about the symptoms, incidence, progression of infections, incubation and elimination period and other factors of the virus COVID-19.

These questions have their own field of study. Epidemiology is the biomedical science that is responsible for studying the distribution, frequency and conditions for the appearance and progression of a disease, and then we will see more in depth what it is about.

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What is epidemiology?

Epidemiology, (from the Greek "epi", "about; "Demos", "people"; and "logos", "science") is the study of the appearance and distribution of events, states and processes related to health in the population. That is to say,

it is the medical science that studies diseases and their evolution in the population as a whole. Epidemiologists study the distribution, frequency, and factors that influence and determine the progression of diseases in a group of people.

The position of epidemiology in the biomedical sciences is very important, since bridges the gap between the health sciences and the social sciences. It integrates both biomedical and social methods and principles to study health, control diseases in the population, and study their socio-economic and biomedical effects.

Although originally epidemiology arose to study infectious disease epidemics, such as cholera, the Spanish flu or plague, today diseases not necessarily due to bacteria and viruses are also included, such as lung cancer cause of smoking, addictions, in addition to the appearance of mental disorders such as bipolar, anorexia nervosa or depression, among others.

What is taken into account when studying diseases?

Epidemiologists, when studying a disease, whether caused by a live pathogen such as bacteria or by habits in the population, such as sedentary lifestyle and smoking, take into account a series of patterns of the medical or psychiatric condition to to study:

1. Weather

With time refers to when it arises, especially if it is a disease with a possible contagious cause, being able to have its highest points at a certain time of the year.

2. Place

It is the physical place, like a city, a country, the characteristics of the area where there have been more cases…

3. Persons

With people, reference is made to those who are more likely to manifest a certain biomedical condition, that is, the risk group.

Typically, in contagious diseases, the groups most at risk are newborns and the elderly.

Epidemiological methodology

The epidemiological methodology uses the observational scientific method because this discipline, to increase its knowledge, has to use real cases that occurred in the population. That is, look at how many new cases of the disease there are, what individual characteristics make those cases have manifested the disease, what has made that in another place there has not been so much incidence…

The epidemiological method uses mainly quantitative techniques. Epidemiological studies do not alter or manipulate the factors that act on people, unlike a laboratory experiment, in which the characteristics of the person, the type of stimuli or environmental factors to which they are subjected, among others, are controlled.

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objectives

Epidemiology is a fundamental area of ​​biomedical sciences, since it allows us to know the development of medical conditions, whether or not they are caused by infectious agents. This discipline has the following objectives.

1. Establish the magnitude of the disease

Aims to measure what happens in the population, what are the rates of mortality, incidence and prevalence of diseases, in addition to the prevalence of risk factors.

All this serves to know the specific characteristics of health or disease in a population, in addition to being able to monitor over time how changes are taking place in these features.

For example, epidemiology would study why in a certain region there is more mortality than in another, what genetic factors and environmental factors make a population more vulnerable or what eating habits or that imply risk would explain the incidence of medical condition.

2. Identify the determinants of the disease

As we have already seen, since its inception, epidemiology has tried to discover the reason for the appearance of a certain state of health and what causes affect the pathological process.

In essence, is responsible for identifying factors that imply risk when it comes to manifesting a medical illness or a psychological disorder.

3. Complete clinical charts

In clinical medicine, epidemiology has a very useful application, since it allows to specify, by means of epidemiological and statistical criteria, what the patient is suffering.

An example of this was the case of rapeseed oil poisoning. Through epidemiological research, it was possible to discover that the disease manifested by thousands of people was caused by consuming that particular oil.

4. Detect new diseases

The appearance of new cases of an unknown disease is studied using the epidemiological method.

This was the case with HIV / AIDS. Patients were found to develop a rare pneumonia, which only affected people who had symptoms of immunosuppression.

5. Evaluate the effectiveness of the health intervention

Epidemiology It is applied to know the effectiveness of any type of health intervention, either prevention or treatment.

6. Contribute to health planning

Although the above applications already contribute to health planning, epidemiology is also used, of specific way, to know the specific needs of the health services, for example, designing plans of Health.

Besides, also It is used for the evaluation of results after health intervention policies, analyzing the objectives set in the previous plans.

7. Contribute to training

Epidemiology not only seeks to find out how a disease occurs, what is its prevention, what population is at risk and other aspects directly related to the biomedical condition.

Too aims to train healthcare professionals so that, in case the disease appears, they know, consulting the biomedical literature and knowing the symptoms of a health condition in question, what they should do and how to prepare.

Some fundamental terms

Within the language of epidemiology, some terms are collected that have a specific meaning when talking about pathological processes. We will take a closer look at some of them below.

1. Epidemic

A disease is considered an epidemic when there is a very high number of people who present this medical condition simultaneously.

2. Pandemic

A pandemic is an epidemic of great proportions, which spreads widely, becoming present throughout the world. An example of this is the case of COVID-19 in March 2020.

3. Endemic disease

An endemic disease is one that occurs with the greatest number in a certain population, although it does not necessarily imply that it has manifested itself in all individuals.

An example of an endemic disease is the case of thalassemia, a type of anemia found in many Mediterranean countries, with more cases being found in southern Spain and Italy.

4. Incidence of a disease

This term refers to the number of new cases of an individual disease in a population for a certain period of time.

5. Prevalence

The prevalence of a disease is given by the total number of new and existing cases detected in a specific population, also for a certain period of time.

6. Outbreak

An outbreak is understood as the appearance of new cases in a specific region, generally during a short period of time.

When we speak of an outbreak, it is indicated that there are more cases than previously, although it does not necessarily have to refer to the appearance of a new disease. It may be that the same disease occurred previously, but very sporadically.

About contagious diseases

To cause disease, a pathogen, such as a bacterium or a virus, needs to find an individual to host. There, grows and reproduces, affecting the health of the individual and producing the symptoms of the disease.

It should be said that, although there are diseases that are fatal, in most contagious diseases, if the host dies, so does its tenant, which is not beneficial. If they have to kill the host, these organisms must first be able to reproduce and pass to another organism, because otherwise they will end up becoming extinct.

It is for this reason that most host-dependent pathogens need to adapt and coexist with the host individual. It is not a symbiotic relationship, but a parasitism, since the host individual, even if he does not die, will be harmed.

The pathogen, when it is well adapted in the individual, takes what it needs to be able to continue living and uses the structures biological characteristics of the host to nourish or reproduce, as would be the case of viruses with cells during reproduction viral. The damages that these pathogens can cause are various, ranging from simple temporary symptoms to chronic infections that must be treated urgently and intensely.

Bibliographic references:

• Hernández-Aguado, Ildefonso, Lumbreras, Blanca, & Jarrín, Inmaculada. (2006). The epidemiology in the public health of the future. Spanish Journal of Public Health, 80 (5), 469-474. Retrieved on March 19, 2020, from http://scielo.isciii.es/scielo.php? script = sci_arttext & pid = S1135-57272006000500005 & lng = es & tlng = es.
• Fernández, E. (s. F.). What is epidemiology for? esteve.org. Recovered from https://esteve.org/wp-content/uploads/2018/01/13113.pdf.