The 14 types of fever (and body temperature levels)

Fever is one of the most common experiences in the life of practically every human being with time to develop, and is linked to a wide variety of health disorders. That is why it is important to understand this phenomenon and know how to identify the types of fever that exist.

In this article we will see what types of fever exist according to different classifications, and as well as their characteristics and possible health hazards.

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What is fever?

Fever, the increase in body temperature, occurs as a reaction of the body to an agent identified as a pathogen, in order to eliminate it and activate the immune system.

Thus, fever acts as a sign that tells us that something in our body is not going well and also promotes the non-proliferation of germs, since these normally only grow at normal temperatures between 35.5 and 37°C; we will consider fever when the temperature is above 38 °C, this being assessed as urgent when it exceeds 41 °C. Seen another way, it is considered that the normal temperature of the human body ranges from 35.5 to 37 °C, and may vary depending on the subject.

In this way, Temperatures between 37 and 38 °C constitute what is known as low-grade fever. when it is maintained for 24 hours. If it is higher than 38 °C, it is already considered a fever, at 39 °C the fever is classified as moderate, and at 40 °C it already indicates an emergency situation.

We say that an individual has a fever when we observe an increase in his body temperature, hyperthermia; this occurs in the presence of a potential pathogen, usually an infection. This increase in temperature tells us that our immune system has been put into operation to combat these elements that "have sneaked" into the body; therefore, it works as an alarm to act if we see that this feverish state does not improve, and also as a defensive mechanism to kill certain harmful microbes.

The characteristic symptoms of fever are: headache, muscle pain, chills and drowsiness. In general a feeling of tiredness and exhaustion arises.

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The types of fever (classified and explained)

There are different types of fever that we will classify according to their intensity, duration, temporal pattern, cause, and how it started. We have already introduced the classification of fever according to intensity in the previous section. We have: low-grade fever if the temperature is between 37 and 38 °C, fever between 38 and 41 °C, and hyperpyrexia if it exceeds 41 °C.

We must take into account how we take body temperature, since depending on the instrument we use, it may vary.. Thus we can measure it in different parts of the body such as in the mouth (oral), through the rectum, in the armpit, in the ear or on the forehead. The most accurate are considered to be the ones we take orally or rectally; in the other three, which are more frequent, they show less exact results. For this reason, it will be necessary that when we communicate our temperature to the doctor, we indicate with which measuring tool we have taken it.

Below we will see some of the types of fever that are considered according to the aforementioned variables.

1. Types of fever according to its duration

Depending on how they evolve and how long the fever lasts, we speak of three types of fever

1.1. acute fever

As its name indicates, this will be the fever that lasts the shortest time, less than 1 week. The usual causes of this type of fever are viral or some type of infection, this type of fever tends to reach higher temperatures or worsen as the day goes on, higher temperature during the night. Examples of acute fever can be skin, respiratory or urinary infections.

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1.2 Subacute or prolonged fever

We speak of subacute fever when the subject has a fever for more than 1 week, but does not exceed 3 weeks. This type of fever is linked to bacterial infections, examples of these could be enteric fevers such as typhoid.

1.3 Chronic fever

Chronic fever exceeds 3 weeks of symptoms. It may be due to one of the previous fevers (acute or subacute) that has not been cured, or to some type of infection that is chronically affected, such as HIV or tuberculosis.

2. Type of fever according to the pattern

According to the temporal pattern that the periods of fever present, we differentiate four types.

2.1 Intermittent fever

As its name indicates, in this type of fever there are variations throughout the day, for 24 hours, giving periods of fever and others without showing high temperature. Examples of this type of fever are abdominal abscesses, caused by a pocket of pus, or malaria.

Within the intermittent fevers we find hectic or septic fever; this is characterized by a large difference in temperature between periods of fever and non-febrile periods; Normally this is due to septic processes where there is dysfunction in the organs due to a deregulation of the infection.

On the other hand, we also find everyday fever, which shows a regular bout of fever every day and is typically caused by some kind of Plasmodium, which is a type of protozoan (for example, malaria can be classified within this type).

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2.2. remittent fever

In the remittent type of fever the high temperature remains high permanently, without reaching normal levels during the day, but variations greater than 1 °C do occur. An example would be brucellosis, a type of bacterial infection that is transmitted from animals to people, being common by eating raw or unpasteurized dairy foods.

23. continuous fever

In the case of continued fever, it happens similar to the previous type of fever; that is to say, the high temperature is maintained throughout the day, but in this case there are no large fluctuations, the difference between maximum and minimum temperature is not greater than 1 °C. A disease that can present this pattern of fever is pneumococcal, which leads to a serious infection by bacteria, specifically Streptococcus.

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2.4 Relapsing fever

Recurrent fever, also called relapsing, periodic or undulating, alternates periods of fever and periods without fever. This definition may be similar to intermittent fever, but unlike this, where the variation occurs in an interval of 24 hours, in the recurrent the interval of variation is greater.

In this way, after a period with normal temperature, the fever reappears, and another type of pattern of those already mentioned may then appear. Within relapsing fever, two types can be differentiated: Pel-ebstein fever, which is characterized by being infrequent and by present a pattern of 3 to 10 days with fever followed by 3 to 10 days without fever and so on continuously and tertian, quartian and quintana febrile intervals followed by two (tertian), three (quartian) or four (quintana) days with temperature are observed in these types. normal.

3. Type of fever according to its cause

As we have already pointed out before, the increase in fever is due to the appearance of a pathogenic agent that activates the immune system, in this way there can be different causes.

3.1. Fever from infection

Fever due to infection is the most common cause; This can occur in different parts of the body, and can be skin, gastrointestinal or throat.

The increase in temperature is beneficial, since it helps the immune system to activate and function more quickly and, on the other hand, the Most infectious agents develop at normal temperatures between 36-37%, ceasing to proliferate if there is an increase in temperature.

3.2. Fever due to autoimmune involvement

In the autoimmune type of fever the increase in temperature is due to the erroneous interpretation that the immune system makes of its own cells, not recognized as such and for this reason it attacks them. An example is lupus which, among other symptoms, produces a fever with no known cause.

3.3. cancer fever

In this case, the increase in temperature and the activation of the immune system is due to the detection of a tumor that the body interprets as a pathogen and increases its performance to eliminate it.

3.4. vaccine fever

Vaccines have the function of preparing and teaching the body, the immune system, how to act in the presence of certain viruses or bacteria. Thus, it consists of the introduction of some piece of inactive virus or bacteria that usually only cause a mild reaction.

3.5. Tooth growth fever

When the teeth begin to come out, it is common for the child to show discomfort and can even produce an increase in temperature and inflammation as a response of the immune system to protect the subject. Normally, the increase in temperature is slight, giving only low-grade fever.

3.6. Fever as a drug side effect

As a side effect of some medications, an increase in temperature may appear, such as low-grade fever or a few tenths of a fever, although normally, if there are no complications, these disappear when the drug is withdrawn.

3.7. Fever due to blood clots

A clot is a mass of platelets, proteins, and blood cells stuck together. When this body forms in the circulatory system and clogs or is in danger of clogging the veins or arteries, the body activates the immune system. and increases body temperature thus facilitating the removal of the clot.

3.8. Fever of unknown origin

In this type of fever, as its name indicates, the cause is not known, since it is not due to any of the aforementioned affections. If the fever lasts a short time, it will not be a major complication, but if the high temperature persists for more than 3 weeks, that is, it becomes chronic, the doctor will continue to analyze what may be the cause of such deregulation

4. Types of fever according to its onset

Depending on the mode of onset of fever, we will differentiate between sudden or slow onset.

4.1. sudden onset fever

In this case we observe that temperature rise is sudden.

4.2. Slow onset fever

We consider slow onset when the increase in temperature appears progressively.