Abstract

• Fever refers to a body temperature of more than 38.2 °C.
• With the increased temperature, the immune system fights various pathogens.
• With appropriate treatment of the triggering disease, the fever usually also decreases.
• Antipyretics are only useful if the fever lasts for a long time or rises above 40 °C, but are then necessary.

Definition

Normal body temperature in adults fluctuates between 36.5 °C and 37.4 °C. Doctors speak of fever when temperatures exceed 38.2 °C. In principle, fever is not a disease in its own right, but a symptom. The increased body temperature is a defensive reaction of the immune system and serves to combat pathogens and inflammatory factors.

It is advisable to consult a pediatrician for infants with a body temperature of 38 °C or higher in the first three months. Infants under two years of age require medical attention if the fever lasts longer than one day.

Symptoms

Even a slight fever can weaken the body’s performance. Depending on age, gender and general condition, even slightly elevated temperatures of 38 °C can cause considerable discomfort. As the body temperature rises, the symptoms generally intensify.

The typical accompanying symptoms of febrile illnesses include

• Joint pain
• Tiredness and fatigue
• Headache
• Sweating
• Feeling thirsty
• Dry and coated tongue
• Chills
• Loss of appetite

Causes

Flu viruses are one of the best-known causes of fever. Numerous other infections or autoimmune diseases and tumors also stimulate the immune system to increase the temperature. Doctors distinguish between different types of fever:

Note: Body temperature also fluctuates in healthy people. It is lowest in the morning and rises towards the evening.

Diagnosis

As fever is merely a concomitant symptom of various illnesses, a comprehensive diagnosis may be necessary. First of all, detailed information about the patient’s medical history and the course of the fever as well as a thorough physical examination of the patient lead to a suspected diagnosis.

The following methods can then provide decisive indications of the fever trigger:

• Complete blood count
• Urinalysis
• Endoscopy (endoscopy) in the area of the respiratory tract
• X-rays of the chest
• Ultrasound scans (sonography) of the abdominal organs and kidneys
• Ultrasound examination of the heart
• Tissue samples (biopsy) from the liver, lymph nodes or bone marrow
• Special antibody tests
• Malaria rapid test
• Tuberculin test

Treatment

An elevated body temperature weakens common pathogens. This is because viruses and bacteria adapt to the normal body temperature of 36 to 37 °C. Treatment therefore focuses on the disease causing the fever.

The following measures can alleviate the symptoms that are only caused by the fever itself:

Tip: Sweating increases the need for fluids. If you have a fever, your body needs half a liter to one liter of additional fluid for every degree above 37 °C every day. Water or unsweetened fruit and herbal teas are suitable.

Questions and answers

When is a fever dangerous?

With a fever of over 40 °C, the body can no longer regulate temperature deviations on its own. In this case, medical treatment with antipyretic medication is necessary. A body temperature of more than 42.6 °C is life-threatening: the heat damages nerve cells and causes proteins in the body to coagulate.

Which thermometer is suitable for taking a temperature?

Two main groups of thermometers are suitable for accurately measuring body temperature:

• A conventional glass contact thermometer provides reliable results when taking a temperature in the bottom or under the tongue. Electronic contact thermometers transmit the data digitally in a shorter measurement period.
• Infrared measuring devices such as an ear thermometer measure the temperature directly at the eardrum. This method is not suitable for newborn babies or those with middle ear infections. In this case, infrared rays measure the temperature with a forehead thermometer. However, this variant leads to measurement inaccuracies.

Where is the measuring accuracy of a clinical thermometer most effective?

Taking a temperature rectally in the bottom has proven to be the most reliable method. The measurement result under the tongue is around 0.5 °C lower. When measured in the eardrum, the result is 0.5 to 1 °C lower than the rectal measurement. At the temple, the measured value deviates by more than 1 °C. Inaccuracies of up to 2 °C occur under the armpit.

How does heat stroke differ from a fever?

During a heat stroke, the temperature rises to more than 40 °C. The lack of sweating and uncontrolled heat production in the body can cause a life-threatening build-up of heat. In addition to the general symptoms of fever, signs of heat stroke include severe cramps, loss of consciousness, rapid heart rate and low blood pressure.

The following steps are necessary as initial measures:

• Move the patient to a cooler environment
• Call an ambulance
• Cool the body (e.g. with cold, damp cloths)
• Administer liquid
• If unconscious, place in recovery position

When does a fever require a sick note?

Fever and accompanying symptoms reduce concentration. The doctor treating you will certify that you are unfit for work for the entire duration of the elevated body temperature. If, for example, there is a risk of infection for colleagues or people under your care – for example in schools or nurseries – sick leave is even mandatory. Anyone who goes to work anyway may face heavy fines.

Sources

• https://www.apotheken-umschau.de/Fieber
• https://www.aerzteblatt.de/archiv/125845/Leitsymptom-Fieber
• https://www.internisten-im-netz.de/krankheiten/fieber/was-ist-fieber/
• https://www.internisten-im-netz.de/krankheiten/fieber/temperatur-regulation-im-koerper.html