92 more Covid-19 deaths have been recorded in South Africa which brings the total to 2 749, while cases now stand at 159 333 an increase 8 124 Picture: Tracey Adams/African News Agency (ANA)

Experts say fever screening is not effective

CAPE TOWN- As South Africa eases the lockdown restrictions, various Covid-19 health and hygiene practises have been implemented in order to curb the spread of the virus. These practices include physical distancing, hand sanitising, the wearing of masks and fever screening.

Experts say that fever screening – which is now a requirement before entering into hospitals, shops, workplaces and schools  –  is unlikely to reduce the spread of the virus.

Physiology professor from the University of the Witwatersrand, Andrea Fuller and professor in the School of Human Sciences from the University of Western Australia, Duncan Mitchell outline the physiological and clinical reasons why fever screening is not effective. 

In an article published in The Conversation, Fuller and Mitchell say that infrared thermometers cannot detect Covid-19 and many people who test positive, especially children, do not have a fever. 

Fever is a temporary increase in average body temperature above 37°C, and persons with a high fever can have a temperature of above 38°C. The body develops a fever as part of a defensive response to infection by a virus.

To detect a fever, a reading of the body core temperature is required and the most accurate readings are taken from either the mouth or the rectum. 

Fuller and Mitchell say there are limitations to infrared thermometers or thermal cameras for detecting fevers because they measure heat radiating from a surface otherwise known as the surface temperature, but they don’t measure body core temperature.

Human surface temperature can be influenced by environmental conditions. Persons in cool environments can have a surface temperature lower than their body core temperature. Those exposed to the sun, or doing exercise can have a high temperature reading above their body core temperature.

Fuller and Mitchell suggest that scientists should have been forthright about the value of fever screening, and that border screening for infectious diseases should not be continued.

“The data from Ebola shows the same pattern. Not one case of Ebola virus infection was picked up in 166 242 airport passengers screened when entering and leaving Sierra Leone in the 2014/2016 outbreak,” said Fuller and Mitchell.

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