There has been a big focus on temperature screenings, as a fever can be one of the first symptoms of coronavirus disease 2019 (COVID-19) infection. Both the United States Department of Health and Human Services (DHHS) and the Centers for Disease Control and Prevention (CDC) recommended for individuals with a temperature greater than 100.4°F to self-quarantine for 14 days.
In a perspective piece published in Open Forum Infectious Diseases, the authors questioned the most appropriate temperature cut-off to define a fever and the best method for assessing COVID-19 fevers.
Data showed that when stratified by temperature, less than half of patients positive for COVID-19 had temperatures greater than 102.2°F (9%) or 100.6°F to 102.2°F (34%). Furthermore, the term “body temperature” is vague, as temperature varies by anatomical site. In general, axillary temperatures are lower than oral temperatures which are lower than rectal temperatures.
Since the beginning of the COVID-19 pandemic, non-contact infrared thermometers have become more common in clinical and public settings due to the ability to assess temperature while maintaining physical distance. However, among 46,000 travelers screened by infrared thermometers at airports in the United States, only a single COVID-19 infection was detected.
Some reasons for this apparent failure for mass screenings included the fact that several biological features alter temperature including gender, ethnicity, and circadian rhythm. Environment factors such as make-up, sweat, distance between device and subject, ambient air temperature, and humidity can alter non-contact infrared thermometer accuracy.
Overall, the current data indicated that COVID-19 fever cutoffs should be reevaluated. On the basis of results from a single study evaluating forehead temperatures among healthy adults, study authors suggested a cutoff temperature of greater than 96.1°F. However, because 40% to 45% of COVID-19 infections are asymptomatic, any mass temperature-screening program is likely to fail.
The perspective authors speculated that perhaps a more prudent mass-screening program should include innovative public health surveillance tactics involving group testing or data from wearable devices. However, current non-contact infrared temperature screenings for COVID-19 have not been successful.
Wright WF, Mackowiak PA. Why temperature screening for covid-19 with non-contract infrared thermometers doesn’t work. Open Forum Infect Dis. Published online December 14, 2020. doi:10.1093/ofid/ofaa603.