Non-contact infrared thermometers are not a very effective tool for screening people infected with Covid-19.
- Checking the temperature with an infrared thermometer does not reflect the true body temperature.
- Infrared thermometers give misleading readings throughout a fever.
- As of February 23, 2020, more than 46,000 travelers have been screened with infrared thermometers at US airports and only one person has been identified as having SARS-CoV-2.
Fever is one of the most common symptoms of people infected with Covid-19. But taking the temperature as a means of screening for the SARS-CoV-2 virus is a bad strategy, warn American researchers from Johns Hopkins University and the University of Maryland School of Medicine. This is all the more true, they add, as it is usually done with an infrared thermometer at the forehead which cannot detect the exact temperature inside the body. These findings were presented Dec. 14 in the online journal of theInfectious Diseases Society of America.
Only 1 positive person out of 46,000
Checking the temperature with an infrared thermometer does not reflect the true body temperature. “Temperatures obtained with infrared thermometers are influenced by many human, environmental, and equipment variables, all of which can affect their accuracy, reproducibility, and relationship to the closest measurement of what might be called ‘temperature’. body’ – the core temperature or the temperature of blood in the pulmonary veindetails William Wright, assistant professor of medicine at the Johns Hopkins University School of Medicine and co-author of the study. The only way to reliably measure core temperature requires catheterization of the pulmonary artery, which is neither safe nor practical as a screening test.”
The researchers provided statistics that show why using this method of taking temperature as a screening test is a bad strategy. “As of February 23, 2020, more than 46,000 travelers have been screened with infrared thermometers at US airports and only one person has been identified as having SARS-CoV-2notes William Wright. In a second example, CDC staff and US customs officials screened approximately 268,000 travelers through April 21, 2020, finding only 14 people with the virus..”
Different level of temperatures during a fever
A CDC report from last November showed the very low ratio of infrared thermometer screening. Of the more than 766,000 travelers screened on American soil between January 17 and September 13, a ratio of 1 in 85,000, or approximately 0.001%, subsequently tested positive for SARS-CoV-2. Only 47 of 278 (17%) people in this group with SARS-CoV-2-like symptoms had a measured temperature that met CDC criteria for fever.
The other problem pointed out by the researchers is that infrared thermometers give misleading readings throughout a fever, making it difficult to determine when a person actually has a fever or not. “During the period when the fever is rising, a rise in core temperature occurs which causes the blood vessels near the surface of the skin to constrict and reduce the amount of heat they give offsays William Wright. And during a low fever, the opposite happens. So basing a fever detection on infrared thermometers that measure heat radiating from the forehead may be totally irrelevant..”
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