Fever is a common and common symptom. Normal body temperature is assumed to be 36.6 °C. It is correct, as long as it is measured in the armpit with a traditional electronic thermometer, mercury or liquid crystal thermometer (currently, mercury thermometers have been withdrawn from use; mercury has been replaced with a metal alloy, used in the so-called liquid crystal thermometer).

More accurate is the measurement in the mouth – three lines higher – or the measurement of rectal warmth (measured in the rectum, especially in young children, this measurement is very accurate). Correctly, it is five strokes more than under the armpit. An identical result (37.1 ° C) is obtained by measuring the temperature in the ear on the tympanic membrane. This assessment takes little time and is therefore readily used in hospitals, but it must be remembered that this measurement is sometimes inaccurate due to the presence of earwax.

We assume that the starting point is a careful measurement of the temperature in the armpit, and its correct value is 36.6 ° C. The absolute condition of “careful” measurement is a strong pressure of the thermometer under the arm by the sick person and a sufficiently long measurement time – in electronic thermometers, sound signaling is sometimes helpful.

There is also a problem with the strict definition of fever.We assume that a fever is considered to be a body temperature above 38.0 °C. The range of 37.1–38.0 °C is known as low-grade fever.

What is the biological significance of fever? How is it made?

Fever is one of the body’s primary defensesand has been developed as a non-specific support for the immune system in response to an attack by infectious agents (bacteria, viruses, fungi, parasites, etc.). Very often, a patient develops a local inflammatory reaction in the gates of infection (e.g. the throat in streptococcal angina, the intestines inamoebiasis,or amoebiasis, or the liver in the course of hepatitis), to which the body reacts additionally with a general symptom (systemic, affecting the whole organism), what is fever. At higher temperatures, many bacteria reproduce less well, and some even die.

However, it should be remembered thatfever is a very non-specific symptom of the disease, which does not mean that the body has been attacked, but rather that the body has decided that it has been attacked. This is an important distinction. Increased body temperature is, as mentioned, a systemic symptom of any inflammatory reaction, and therefore most often the result of an infection (by bacteria, viruses or parasites). However, it also occurs when the inflammation is caused by:

• allergic, i.e. when the immune system mistakenly recognizes foreign, but completely harmless factors, i.e. antigens, as dangerous and takes an unnecessary fight (this is the essence of allergies);
• autoimmune, when a mistake of the immune system consists in recognizing its own fragments, i.e. antigens (so-called autoantigens) as foreign and dangerous; the problem is more serious than in allergic diseases, because in the latter, cure is often achieved by eliminating allergens from the environment, while in the case of autoantigens, such elimination is not possible;
• “sterile” inflammation, that is, inflammation that occurs in tissue despite the absence of any infection; an example of this group of causes of fever is a completemyocardial infarction: cells in the infarction area die, the focus of the infarction becomes dead and is then recognized as a foreign body, causing inflammation (locally) and general symptoms, including fever.

Prolonged fever can also be an important symptom of anoveractive thyroid glandorcancer.

In the course of fever:

• the skin’s blood vessels shrink (that is why a person with a fever is pale, he then gives less heat through the coatings and saves it);
• skeletal muscles begin to tremble (popular chills); as always, significant amounts of heat are released when the muscles work;
• the muscles around the pubis (“goose bumps”) tighten;
• fat is burned, especially so-called brown fat;
• the activity of thyroid hormones increases, thanks to which, in simple terms, the energy generated in the metabolic processes in the body is not used effectively (e.g. for work or the synthesis of chemical compounds), but is dispersed in the body in the form of heat.

Another condition with elevated body temperature is hyperthermia. The temperature rises to very high values​​(40–42 ° C), which is not subject to negative feedback (like a thermostat that has broken down). Hyperthermia is a life-threatening condition as the body overheats dramatically. Persistently high body temperature can damage the functions of proteins and cell membranes, damage and die of cells (including brain neurons), failure of many organs of the body and death.

Examples of causes of hyperthermia are brain damage in heat stroke (sunburn), vascular changes of the brain (embolism, stroke) or cancer (damaging the thermoregulatory center), as well as the action of some rarely used drugs – for general anesthesia during surgery – in hypersensitive people. The underlying cause of the hypersensitivity is genetic, and the syndrome itself is known as malignant hyperthermia.

Some characteristic forms of low-grade fever and fever

Physiologically, low-grade fever is common during pregnancy and in the second phase of the menstrual cycle, as well as in physical exertion and emotions when the sympathetic system is at work.

It should be remembered that in most people, due to the daily cycle of life activities, the body temperature is a few bars higher in the afternoon than in the morning (the traditional value of 36.6 ° C usually refers to the morning measurement). In people with a fever, this characteristic, the fever path, is usually preserved and the body temperature in the afternoon is about 1-1.5 ° C higher than in the morning – this is the typical fever path. If this path is different, the fever is defined as:

• constant – the difference between morning and evening temperature is less than 1 ° C,
• etching – difference over 2 ° C; its extreme type is hectic fever (difference over 3 ° C), and the morning temperature is often correct or even lowered;
• intermittent (or periodic) – fever every third or fourth day;
• bactrian, the appearance of high fever for a few days, then after a short improvement with a low-grade fever – again high body temperature, with the daily routine being usually typical.

What to do in case of a fever?

The procedure is determined by: the circumstances of the occurrence of fever, the course and speed of its increase, and accompanying symptoms (especially the general condition of the fever). Always see a doctor if you or your family are in doubt about what to do.

The short-term increase in body temperature is generally not a cause for concern. As a rule, its cause is a common infection,coldorfood poisoning. Usually the symptoms of, for example, purulent angina,pneumonia, acutediarrheaand viral infection are so characteristic that they come to the fore. The increase in temperature is a natural symptom of the body’s defense, which responds properly to the infection. Fever completes the picture of the disease here, so it requires unconditionally visiting a doctor, taking the prescribed medications and usually staying in bed.

A different procedure applies to four clinical situations.Firstlywhen the fever is not high (up to 39 ° C) and – apart from the feeling of breakdown, muscle aches and headaches – there are no other symptoms of the disease, and the patient’s condition is good. In this case, a viral infection is most likely. You may consider abstaining from your doctor’s appointment, administering over-the-counter antipyretic drugs (eg, acetylsalicylic acid, ibuprofen, paracetamol), and bed rest. Use common sense, and you can also rely on previous experiences (e.g. parents know their children’s sensitivity to common infections, in some people similar harmless ailments repeat over the years, etc.). Usually, a fever that lasts for about a week (5-7 days) does not necessarily mean a serious illness, because this is the time needed, that the immune system produces specific antibodies and cells that precisely destroy the infectious agent. On the other hand, if the fever and accompanying breakdown do not decrease and the temperature only drops with medication and then recurs, see a doctor.

Secondly, the fever that accompanies very serious symptoms and the serious condition of the patient must cause anxiety. Here are some specific examples:

• severeheadachewithimpaired consciousness;
• cough, runny nose, conjunctivitis withphotophobia, bactrian fever;
• angina (purulent inflammation of the pharynx and tonsils) with a mottled red rash;
• shortnessof breath , dry or moist cough, oftenchest pain;
• nausea, vomiting, stool and wind retention, severe stomach pain;
• burning sensation when urinating, frequent urination and sometimes a bloody color, sometimes pain in the lumbar region;
• relatively mild fever, with indigestion, vomiting, discolored stools and jaundicewhich develops over several days .

Each such condition requires immediate medical consultation and, if necessary, hospitalization.

Thirdly, any fever, even a low (below 39 ° C), which is not accompanied by characteristic symptoms and lasts a long time, causes serious concern, so it cannot be referred to as a “banal viral infection”. For such conditions, the concept of fever of unknown cause has been introduced. It is diagnosed when it exceeds 38 ° C and lasts longer than three weeks. In this case, you should immediately see a doctor.

Fourth, a very small number of patients develop very high body temperature very quickly, and this is the hyperthermia described above, not a fever. Therefore, any increase in body temperature above 40 ° C requires quick and vigorous action: administration of acetylsalicylic acid (1g) or paracetamol (1g) and plenty of cold fluids, and if that is not enough, cover the patient with wet cold sheets or ice and use cool baths. It is necessary to report to the emergency department or call an ambulance.

To sum up, fever can be both a symptom of the body’s natural defense against a harmless infection and a symptom of a serious, life-threatening disease.

How is the diagnosis made by a doctor in relation to fever?

The doctor collects an interview, examines the patient and, if necessary, orders additional tests. The latter are usually not needed in the case of typical disease symptoms (angina, food poisoning,bronchitis), especially when the patient is in good condition and does not require hospitalization.

Accompanying symptoms should be described to the doctor in detail, for example headache, abdominal pain, severe muscle pain, back pain, cough. You should also tell about the circumstances that may contribute to the development of certain diseases, such as a recent trip abroad, especially to tropical countries, tick bites, taking medications, including over-the-counter medications, and even herbs.

When examining a patient with fever, the doctor pays attention to skin rashes, the condition of the mucous membranes, salivary glands, auscultation changes over the lungs, heart, local or generalized pain in the abdominal cavity or loins, local pain andswellingof the lower limb, sometimes with redness along the vein, pain, redness, warming and swelling of the joints. As a rule, in infectious diseases, lymph nodes are enlarged.

When diagnosing the disease behind your fever, your doctor may order laboratory tests. If an infection is suspected, peripheral blood counts with a white blood cell smear are oftenperformed. Another frequently performed analysis is a urinalysis. It is often supplemented with aurine culturealong with an antibiogram to determine which drug is best for the patient. In addition, the doctor may order other tests, depending on the suspected cause of the fever (eg CRP, ESR, ALT, AST,amylase, rheumatoid factor).

In the event of diagnostic problems, usually already in a hospital setting, the doctor orders microbiological tests, such as blood cultures for aerobic and anaerobic bacteria, sputum tests fortuberculosisand other bronchial tree infections (sometimes with an antibiogram), cerebrospinal fluid tests or tests. serological specific for individual infectious agents (viruses, bacteria and parasites).

He may also order additional imaging tests, such as abdominal ultrasound, cardiac echocardiography,computed tomographyand magnetic resonance imaging of areas suspected of being the cause of the fever, sometimes bone scintigraphy and ultrasound examination of the vessels.

What are the treatments for fever?

The circumstances under which you can cope with a fever alone at home are listed above. It should be emphasized that the fight against this symptom has limited sense, as long as you do not know its cause. Action should be based on a simple assumption, both for the patient at home and for the doctor in the clinic or hospital: fever is a defense mechanism, so the goal of treatment is to reduce it, not to bring it back to normal. A fever that is too high is a severe symptom that is difficult to bear. If it lasts a long time, it leads to the patient’s cachexia. Therefore, antipyretics should be administered, but the patient should be monitored all the time to make sure that there is a common infection or to undertake more intensive and more detailed diagnostics.

In conclusion, a physician treats a patient with a fever by identifying and treating the cause of the fever.

What to do after treatment ends and to avoid fever?

Some of the diseases that cause fever require recovery after treatment. Follow your doctor’s instructions for what to do after an illness causing fever.