Fever: stages, symptoms, causes, treatment

What is a fever? The stages of this condition, the causes and symptoms will be discussed below. Also we will tell you how to treat the disease. fever stage

Definition of medical term

Nonspecific pathological processes characterized by a temporary increase in body temperature due to the dynamic adjustment of the thermoregulatory system under the influence of pyrogens( i.e., elements that cause fever) are called fever. In medicine, it is believed that this state arose, as a protective-adaptive reaction of a person or an animal to infection. It should also be noted that fever, the stages of which will be listed below, is accompanied not only by an increase in body temperature, but also by other phenomena characteristic of an infectious disease.

The essence of the fever syndrome

It is not a secret for anyone that many infectious and viral diseases are accompanied by an increase in the body temperature of the patient. Moreover, before all the diseases that occurred in this way, called a fever. However, experts argue that in modern scientific understanding such a condition is not a disease. But, despite this, in some names of nosological units the term is still present( for example, Ebola haemorrhagic fever, pappataci fever, spotted fever of the Rocky Mountains and others).

Why does the temperature rise in this or that disease? The essence of fever is that the device for thermoregulation of humans and higher homoiothermic animals responds to specific substances called pyrogens. As a result, a temporary shift of the homeostasis setting point( temperature) occurs to a higher level. In this case, the mechanisms of thermoregulation are preserved. This is the fundamental difference between hyperthermia and fever.

Causes of a fever

Why does the temperature rise in a person or animal? There are a great many causes of fever development. However, the most common are the following:

  1. Microbes, infectious and pathogenic viruses, parasites. Their life products and constituents are pyrogen-chemical substances that act on the center of thermoregulation.
  2. Non-infectious causes. Among them, exogenous proteins are isolated: vaccines, serums, venom of snakes, transfused blood and so on. The native proteins of a living organism also belong here, which changed their properties as a result of burns, trauma, tumor disintegration, and hemorrhage into tissues.

pathological processes

Other causes of febrile syndrome

Why does a fever occur? A disease that provokes an increase in body temperature may be associated with a heat exchange disorder in the violation of vegetative work in adolescents, children and young women( that is, with a thermoneurosis).Also, fever can occur under the influence of the following factors:

  • Taking certain medications. Experts argue that a number of medicines can affect the center of thermoregulation, causing a slight increase in body temperature.
  • Hereditary disorder in the process of thermoregulation. For example, some completely healthy children are already born with a temperature of 37.2-37.4 degrees. For them, this state is the norm.
  • Subfebrile temperature often occurs due to overheating, regular physical exertion, staying in a stuffy room and intense heat.
  • Emotional stress and stressful situations are often accompanied by increased heat production and activation of the hypothalamus, which contributes to the development of fever.
  • The increase in the hormone progesterone in pregnant women also causes a slight increase in temperature. However, there are no other signs of a viral or infectious disease. This condition can be held until the end of the first trimester. However, some representatives of the weaker sex subfebrile temperature accompanies almost the entire pregnancy.

viral diseases

What are pyrogens?

As mentioned above, infectious and viral diseases very often contribute to a rise in body temperature. It happens under the influence of pyrogens. It is these substances that get into the body from the outside or form directly inside, cause a fever. Most often, exogenous pyrogenes are elements of infectious agents. The strongest of these are thermally stable capsular lipopolysaccharides of bacteria( Gram-negative).Such substances act indirectly. They contribute to the displacement of the set point in the thermoregulatory center of the hypothalamus. Most of them have a leukocyte origin, which directly affects other important symptoms of the disease. The source of pyrogen is the cells of the human immune system, as well as granulocytes.


stages In the process of development, fever passes through three main stages. On the first - the person raises temperature, on the second - it is held for a while, and on the third - gradually decreases, reaching the initial one. About how such pathological processes occur, and what symptoms they are inherent, we will discuss further. temperature 35

Temperature rise

The first stage of fever is associated with the restructuring of thermoregulation, as a result of which the heat production begins to significantly exceed the heat transfer. Restriction of the latter is due to a decrease in the influx of warm blood into the tissues and narrowing of the vessels at the periphery. More importance in such a process has a spasm of cutaneous vessels, as well as the cessation of sweating under the influence of the sympathetic nervous system. Symptoms of fever in the first stage are the following: blanching of the skin and lowering its temperature, as well as limiting heat emission due to radiation. Reducing the formation of sweat does not allow heat to escape through evaporation.

Reduction of muscle tissue leads to the manifestation of the phenomenon of "goosebumps" in humans and ruffling of wool in animals. Subjective feeling of chills is associated with a decrease in skin temperature, as well as irritation of cold thermoreceptors located on the skin. From them, the signal enters the hypothalamus, which is the integrative center of thermoregulation. After this, he informs the cerebral cortex of the situation where human behavior is formed: he begins to wrap up, take appropriate postures, etc. The decrease in the temperature of the skin is also explained by the muscular tremor of a person. It is caused by the activation of the tremor center, which is localized in the medulla oblongata and the medulla.

Temperature holding

The second stage of fever begins after reaching the set point. It can take several hours or days, and also be prolonged. At the same time, heat transfer and heat production balance each other. Further increase in body temperature does not occur. why does the temperature rise

Skin vessels in the second stage are enlarged. Also their pallor goes away. In this case, the covers become hot to the touch, and the chills and shivers disappear. The person at this stage experiences a fever. In this state, the daily temperature fluctuations are preserved, but their amplitude quite sharply exceeds the normal one.

Depending on the degree of body temperature rise, fever in the second stage is divided into species:

  • subfebrile temperature - up to 38 degrees;
  • mild fever - up to 38.5;
  • febrile or moderate - up to 39 degrees;
  • pyretic or high temperature - up to 41;
  • hyperpyretic or excessive - over 41 degrees.

It should be noted that hyperpyretic fever is extremely dangerous for human life, especially for young children.

Temperature drop

Decreased body temperature can be abrupt or gradual. This stage of fever begins after the exhaustion of the stock of pyrogens or the cessation of their formation under the influence of natural or medicinal factors. When the temperature falls, the set point reaches the normal level. This leads to an expansion of the vessels on the skin. At the same time, excess heat begins to be gradually eliminated. A person sweats profusely, perspiration and diuresis intensifies. Heat transfer in the third stage of fever sharply exceeds heat production.

second stage of fever

Types of fevers

Depending on the changes in the daily temperature of the patient's body, fever is divided into several types:

  • Constant is a long and steady rise in temperature, the daily fluctuations of which do not exceed 1 degree.
  • Remitting - noticeable diurnal changes can be within 1,5-2 degrees. At the same time, the temperature does not reach normal values.
  • Intermittent - this pathology is characterized by a rapid and significant rise in temperature. It lasts for several hours, after which it is replaced by a fairly rapid fall to normal values.
  • Exhaustive or hectic - with this type of daily fluctuations can reach 3-5 degrees. At the same time, the ups and downs are repeated several times throughout the day.
  • Perverted - for such a fever is characterized by a change in the daily rhythm with high rises in the morning hours.
  • Wrong - characterized by fluctuations in body temperature during the day without a certain pattern.
  • Recurrent - with this type alternate periods of body temperature increase with periods of normal values ​​that last for several days.

It should also be noted that the temperature - 35 degrees - does not contribute to the appearance of fever. To find out the reasons for this condition, you should consult a doctor.

Common symptoms of fever

Low fever( 35 degrees) does not cause fever, since it is characterized by a rise of more than 37 degrees. Common signs of this pathological condition are:

  • feeling of thirst;
  • redness of facial skin;
  • rapid breathing;
  • aches in bones, headache, unmotivated good mood;
  • poor appetite;
  • chills, trembling, intense sweating;
  • delirium( delirium) and confusion, especially in elderly patients;
  • irritability and crying in children.

the first stage of fever

It should also be noted that sometimes a rise in temperature can be accompanied by swelling and pain in the joints, a rash and the appearance of blisters of a dark red color. In this case, you should immediately contact a doctor.

Treatment of

How to get rid of a condition like fever, the stages of which were listed above? To begin with, the doctor must establish the cause of the rise in body temperature, and then assign the appropriate therapy. If required, the doctor can send the patient for an additional examination. If a serious pathology is suspected, the specialist recommends hospitalization for the patient. Also, to eliminate fever, the patient is advised to comply with bed rest. It is forbidden to dress too warmly.

Patient must drink plenty of fluids. As for food, it shows light and well-digested food. The body temperature should be measured every 4-6 hours. If necessary, you can take antipyretics. But this is only if the patient has a strong headache and also a temperature of more than 38 degrees. To improve the condition, the patient is recommended to use Paracetamol. Before taking this medication, you should carefully read the instructions. If the fever is observed in the child, then it is forbidden to give acetylsalicylic acid. This is due to the fact that such a drug can cause the development of Reye's syndrome. This is an extremely difficult condition, leading to coma or even death. Instead, babies are recommended paracetamol-based medicines for efflorescence: Efferalgan, Panadol, Kalpol, and Tylenol.