Thermographic Screening for the Detection of Elevated Body Temperatures in Detail
Certainly, thermal cameras can neither detect a virus itself nor whether a person is carrying a virus! However, these cameras enable the precise non‐reactive, contactless measurement of surface temperatures while using the technical temperature measurement technology known as thermography or thermal imaging. Hence, they are highly suitable for the quick and easy detection of elevated body temperatures, which can be an indication of a possible virus infection. Such indications must, of course, always be followed by other examination methods that allow a reliable positive or negative statement about the disease and to initiate appropriate actions! The term "detecting a fever" in the sense of a (medical) fever diagnosis is actually not permitted as a designation for the above‐mentioned thermographic recording of elevated body temperatures with thermal cameras under strict observation: One reason is that fever is a complex medical phenomenon. The other reason is that, from a purely formal point of view, the cameras used are "only" technical measuring devices and not medical diagnostic instruments.
Thermography systems measure surface temperatures based on the emitted heat radiation, for example the temperature of the human skin surface. However, this is different from the internal body temperature, the so‐called body core temperature. The temperature of the skin surface depends on the ambient temperature (summer, winter, direct sunlight, and so on). In addition, a light film of water can produce evaporative cooling due to perspiration. Furthermore, beards, haircuts, face masks, etc. cause many areas of the skin on the face to be optically "covered" and the heat radiation cannot reach the camera unhindered. Thus, the skin surface in most parts of the face is rather unsuitable for reliable and repeatable thermographic temperature measurement.