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.

Table of Contents

What is fever?

Fever, an 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 is not going well in our body and also encourages 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 higher than 38 °C, and this will be considered 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.

Thus, 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 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 body temperature, hyperthermia; this occurs in the presence of a possible pathogenic agent, usually an infection This increase in temperature tells us that our immune system has been put into operation to combat these elements that have “snuck in” 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

Types of fever (classified and explained)

There are different types of fever that we will classify according to their intensity, duration, temporal pattern, what cause they have and how they 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 37 to 38 °C, fever of 38 to 41 °C, and hyperpyrexia if it exceeds 41 °C.

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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. It is considered that the most accurate are those that we take orally or rectally; In the other three, which are more frequent, they show less accurate results. For this reason, it will be necessary that when we inform the doctor of our temperature, we indicate which measuring utensil we have taken it with.

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

1. Types of fever according to their duration

Depending on how they evolve and how long the fever lasts, we talk about 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 usually reaches higher temperatures or worsens as the day goes by, with higher temperatures at night. Examples of acute fever can be skin, respiratory or urinary infections.

1.2 Subacute or prolonged fever

We speak of subacute fever when the subject has fever for more than 1 week, but it does not exceed 3 weeks This type of fever is linked to bacterial infections, examples of which 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 chronic infection, such as HIV or tuberculosis.

2. Type of fever according to the pattern

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

2.1 Intermittent fever

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

Among intermittent fevers we find hectic or septic fever ; This is characterized by a large temperature difference between the feverish and non-febrile periods; Normally this is due to septic processes where organ dysfunction occurs due to deregulation of the infection.

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On the other hand, we also find the daily fever which regularly shows an episode of fever every day and is typically caused by some kind of Plasmodiumwhich is a type of protozoan (for example, malaria can be classified within this type).

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 could be brucellosis, a type of bacterial infection that is transmitted from animals to people, and is common when eating raw or unpasteurized dairy foods.

23. Continuous fever

In the case of continuous 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.

2.4 Recurrent fever

Relapsing 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 one, where the variation occurs within an interval of 24 hours, in the recurrent one the variation interval is larger

In this way, after a period with a normal temperature, the fever reappears and another type of pattern of those already mentioned may then occur. Within relapsing fever, two types can be differentiated: Pel-ebstein fever, which is characterized by being rare and presenting 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 quintan fever in these types febrile intervals are observed followed by two (tertian), three (quartian) or four (quintana) days with normal temperature.

3. Type of fever according to its cause

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

3.1. Infection fever

Fever due to infection is the most common cause ; This can occur in different parts of the body, and may be cutaneous, 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 majority of infectious agents develop at normal temperatures between 36-37%, ceasing to proliferate if they are produces an increase in temperature.

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3.2. Fever due to autoimmune involvement

In autoimmune type of fever The increase in temperature occurs due to the immune system’s misinterpretation of its own cells, not recognized as such and for this reason it attacks them. An example is lupus, which among other symptoms produces fever without a known cause.

3.3. Oncology 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 pathogenic agent 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. In this way, it consists of the introduction of some fragment of inactive virus or bacteria that normally only generates a mild reaction

3.5. Tooth growth fever

When teeth begin to emerge, it is common for the child to show discomfort and it can even cause 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 side effect of the drug

As a side effect of some medications, an increase in temperature may appear, such as low-grade fever or a tenth of fever, although Normally, if there are no complications, it disappears when the drug is withdrawn

3.7. Fever due to 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 there is a danger of it clogging the veins or arteries, the body activates the immune system and increases body temperature thus facilitating the elimination 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 conditions. If the fever lasts a short time it will not cause any major complications, 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.