Tuesday, September 8, 2020

The Effectiveness of Temperature Screenings to Control the Spread of COVID-9

Airports and border entry points around the world are using non-contact body temperature scanning devices to ensure that people with COVID-19-related symptoms are detected.  Unfortunately, recent research would suggest that this effort is futile.

In a commentary in the September - October 2020 Travel Medicine and Infectious Disease  by Michel Bielecki et al entitled "Body temperature screening to identify SARS-CoV-2 infected young adult travellers is ineffective", the authors look at the efficacy of body temperature screening among young adults.  This is particularly key to controlling the spread of the novel coronavirus since young adults, who are considered by many to be highly contagious when infected with the SARS-CoV-2 virus and are also the most likely population segment to travel and encounter body temperature screenings.

Past studies undertaken during the Ebola and H1N1 influenza outbreak showed that the number of cases detected by screening for body temperature is minimal or non-existent and that SARS-CoV-2 screening procedures in Canada, Singapore and Australia seem to have detected zero cases overall.  Simulations performed modelling COVID-19 suggest that only 44 percent of cases could be detected during screenings using body temperature measurements.

In the study, the authors evaluated the body temperatures of 84 COVID-19 positive patients twice daily for fourteen days after a positive PCR test.  These patients had a median age of 21 and were male recruits in military basic training of the Swiss Armed Forces.  For reference's sake, a normal human body temperature is generally 37 degrees Celsius but can range from 36.1 degrees Celsius to 37.2 degrees Celsius.  The study showed the following:

1.) using a traditional fever cut-off temperature of 38 degrees Celsius, only 18 percent of COVID-19 cases were detected.  

2.) using a higher fever cut-off temperature of 38.5 degrees Celsius, only 8 percent of COVID-19 cases were detected.


3.) using a lower fever cut-off temperature of 37.1 degrees Celsius, 63 percent of COVID-19 cases were detected.  

Using a very low fever cut-off temperature is likely to result in many false positives, particularly if women are included, the subject's temperatures are taken in a warmer climate or there are other respiratory infections present (i.e. common cold rhinovirus) which cause elevated body temperatures.  In addition, by taking Aspirin, acetaminophen or ibuprofen, a person with a fever can significantly reduce their symptoms and negate the risk of being detected as potentially SARS-CoV-2 positive.  The authors of the study also noted that within five days after presenting with a fever, the subject's fever had completely disappeared even though SARS-CoV-2 infectivity remains within 10 to 14 days after infection.  

Here is the conclusion of the study:

"We reinforce the WHO's recommendation that widespread testing for SARS-CoV-2 is currently the only available efficient way to monitor the trajectory of the infection and control the spread of COVID-19. Screening temperature at borders is a strategy that has been pursued in the past and has proved to be both expensive and ineffective. We advocate the evaluation of, novel non-invasive screening approaches, such as testing saliva samples for SARS-CoV-2 with rapid follow-up on positives. This may prove to be a fast and more sensitive alternative to body temperature screening at borders." (my bold)

Let's close with this quote from the United States Food and Drug Administration regarding the use of non-contact temperature assessment during the current pandemic:

"As states and communities implement reopening plans during the COVID-19 pandemic, non-contact temperature assessment devices may be used as part of an initial check at entry points to identify and triage people who may have elevated temperatures. Be aware that, even when the devices are used properly, temperature assessment may have limited impact on reducing the spread of COVID-19 infections. Some studies suggest that temperature measurements alone may miss more than half of infected people.


Thermal imaging systems and non-contact infrared thermometers, which are non-contact temperature assessment devices, may be used to measure a person's temperature. An elevated temperature is one way to identify a person who may have a COVID-19 infection, although an infected person may be contagious without an elevated temperature or other easily detectable symptoms." (my bolds)


In addition, the FDA notes the following:


Non-contact temperature assessment devices are not effective if used as the only means of detecting a COVID-19 infection. Available scientific literature has identified that effectiveness can be limited by several factors, including:


Infections without a fever;

Use of fever-reducing drugs;

Other infections or conditions that may cause elevated temperatures;

Devices failing to identify elevated temperatures, or misreading normal temperatures as elevated;

Failure to follow the manufacturer's instructions for use, such as for set-up, operation, and training.

Despite the clear evidence showing that body temperature scanning is a terribly ineffective means of screening for the SARS-CoV-2 virus, governments (and corporations) around the world insist on using this method as a means of making it appear that they are performing an essential and protective service for their citizens (employees). 

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