The human body is not a static system. Rather, it is a variable that always adapts to different circumstances. This includes body temperature. The core body temperature, i.e. the temperature inside the torso and skull, is kept constant at an average of 36.5° Celsius by control circuits. It is dependent on many influences. On the one hand, it is subject to a diurnal rhythm. Physiologically, the temperature changes during the course of the day with a fluctuation of 0.5-1° Celsius. The minimum is reached around four o'clock in the morning and the maximum around six o'clock in the evening. 1)

Another influencing factor is the female cycle. Hormones such as progesterone, which is increasingly produced in the second half of the cycle, i.e. after ovulation, cause the body temperature to rise by about 0.5° Celsius. The control centre of the body temperature is the hypothalamus. The hypothalamus is a superordinate area of the diencephalon. It serves as a "thermostat" and sets a target value for body temperature, i.e. approx. 36.5° Celsius. Temperature sensors" in the skin or temperature-sensitive nerve cells in the spinal cord and brain stem inform the patient of the current body temperature. If the current actual value does not correspond to the specified target value, the hypothalamus mediates various regulatory mechanisms to adjust the body temperature to the target value. The mechanism of the temperature increase includes, for example, increased muscle activity such as trembling or the burning of fatty tissue. A reduction in temperature, on the other hand, can be achieved by sweating (evaporation) or heat exchange with cooler objects (conduction).1)

In the special case of fever, an increase of the set point in the hypothalamus occurs due to the influence of so-called pyrogens. These can be the body's own signalling substances, such as interleukin 1 or prostaglandin E2, which are secreted by leukocytes (white blood cells) and act as important messenger substances in the immune system in combating various pathogens. But also foreign substances such as pathogen components (exogenous pyrogens) can directly induce a temperature increase via the hypothalamus. Fever is defined as a body temperature of 38° Celsius or higher.1)

Why is fever detection useful?

The measurement of body temperature plays an important role in the diagnosis of various diseases. In the course of the corona pandemic 2019/2020, fever has emerged as probably the most important leading symptom. Various studies have shown that fever is the most common symptom of COVID 19 patients with an occurrence of 83.3 to 87.9% 2)3). Also in the "Report of the WHO-China Joint Mission on Coronavirus Disease (COVID-19)" (February 2020) of the World Health Organization WHO, 87.9% of the patients tested positive for COVID-19 showed fever in a case number of 55924 persons, which is by far the most common symptom of this disease.
But fever is also a common symptom in other diseases. In a Catalan study in which patients with non-specific respiratory symptoms were examined, 86.3% showed fever. Of these, half of the patients tested positive for the influenza virus. They even showed fever in 94.8% of cases. Patients infected with pathogens other than influenza viruses showed fever in 82.4% of cases. Thus, fever was detected as the most common symptom in this study.4)

In the case of COVID 19 infection, one person infected (without legally regulated personal contact restriction) infects between 2.4 and 3.3 other people, who then each infect the same number of people.5) With an influenza disease, one infected person transmits the virus to two other people. This quickly results in an exponential increase in the number of infected people.
The earliest possible detection of infected persons can stop this chain of infection. Since fever has proven to be a common symptom of various diseases and the most common symptom of COVID 19 and influenza patients, there is the possibility to interrupt the infection chains by detecting fever patients.

It should be noted, however, that by no means every infected person also has a fever.
Furthermore, fever can also occur as a late symptom or only in the course of an illness. Therefore, there is no guarantee that a fever measurement will detect all infected persons. A false negative rate, where the infected person has no fever and is therefore not detected by a fever measuring device, is given here as with all diagnostic tests.

Likewise, an elevated body temperature does not always have to be based on an infectious cause. For example, in the case of malignant diseases such as tumour diseases6) or autoimmune diseases7), fever can occur as a reaction of the body and thus poses a risk of false positive results in the sense of an increased body temperature without the risk of infection. Nevertheless, especially in sensitive infrastructures, the detection of even one potentially infectious fever patient could contribute to the interruption of an infection chain. This includes, for example, nursing homes or medical facilities with high-risk patients for whom it is important to be protected from infected persons. Both employees and visitors to the facility could be a possible source of infection, which could be limited by fever screening.

The use of fever measurement could also be useful in various other infrastructures. It is conceivable that it could be used in companies, public authorities, day-care centres, schools or for example for organisers of conferences, festivals or other events with an increased number of people. It could also be used in industries with strict hygiene requirements such as food processing or transport. Before entering the premises, the measurement could be used as access control.

What should be done if a temperature reading with the Kentix SmartXcan gives an increased reading?

The elevated body temperature value should be checked by repeated measurement and, if necessary, supported by another temperature measurement method using a clinical thermometer. It should also be considered whether this person should see a doctor for a physical examination.

After all, only a doctor can make a diagnosis and decide on the further procedure.

List of sources:

  1. Pape/Silbernagel; Physiologie; 2019 Thieme