Are thermal scanners useful and can they detect Covid-19?

Since Covid-19 took over the world, the image of a thermal scanner pointed at a person’s head, wrist or neck has become part of our daily lives. Thermal scanners, also known as temperature guns, have been at the forefront of mass surveillance during the pandemic.

They are used to screen for fever in public places, including malls, markets, offices, restaurants, grocery stores and hotels, but are they useful and can they detect Covid-19?

Thermal scanners are useful in identifying individuals with higher temperatures, one of the symptoms associated with Covid-19.

The World Health Organisation (WHO) says they may not be very effective and can miss people with the disease, or it may show a false positive (fever of a different cause).

“Thermal scanners are effective in detecting people who have a fever (a higher than normal body temperature). They cannot detect people who are infected with Covid-19. There are many causes of fever,” said the WHO.

Prof Cheryl Cohen, the co-head of the centre for respiratory disease and meningitis at the National Institute for Communicable Diseases, said the scanners can be used as a way of protecting people against Covid-19 by picking up cases early.

“So if a person happens to have a fever and we test them and isolate them from society, then this is a helpful part of our defence against the virus,” she said.

Cohen stressed that thermal scanners are not 100% effective and cannot pick up the virus if someone is in the incubation period of the virus. The incubation period is the period between exposure to an infection and the appearance of the first symptoms.

“A person in the incubation period will have the virus in their body but there is no sign that they are sick, they don't have a fever and they can go on to get sick later. So these people can never be picked up by thermal scanners or any other screening tests,” she said.