23.10.2020 change 23.10.2020

PhD students invent ‘coronavirus calculator’ to check effectiveness of face masks

Credit: Adobe Stock Credit: Adobe Stock

A ‘calculator’ that can determine how individual decisions regarding mask selection may affect the number of people infected with the coronavirus has been developed by two Polish PhD students.

The online tool promoting knowledge about pandemic development prevention was prepared by Joanna Michałowska at the Poznan University of Medical Sciences, and Dominik Czernia, PhD student at the Institute of Nuclear Physics of the Polish Academy of Sciences in Kraków.

To use the calculator, you first have to answer the question 'Do you wear a mask?' If yes - select the material it is made of. You can choose covering your nose and mouth with a scarf, a mask made of mixed materials, or one of the three most popular types of masks.

 The authors of the calculator explain that this choice changes an important parameter referred to as the R0 value, or the basic reproduction number of the virus. In the calculator, it is used to calculate the mask effectiveness rate.

 According to the information included in the calculator, fabric masks are cheap and easily available. They limit the inhalation of airborne virus particles and act as a barrier to fluids released when sneezing and coughing. They can be used repeatedly provided they are in good condition and properly cleaned. The Chief Sanitary Inspectorate recommends their use in public spaces. Surgical masks, are more effective as a barrier, need to be changed frequently and cannot be reused. Masks with N95/N99 filters are highly effective (up to 99% depending on the filter), but they are much more expensive than the others and require filter replacement.

The doctoral students assumed that the basic R0 value of the SARS-CoV-2 virus is 2.5 if no restrictions, e.g. masks, are introduced. This means that on average, each sick person infects 2 to 4 people. The calculator assumes that the virus has an incubation period of 5 days.

If the user replies negatively to the question 'Do you wear a mask?', they will learn that their personal choice may lead to the death of 1 person and the development of 20 new infections within 2 weeks.

In the last, third section, the users can determine what percentage of people in society wear masks. After entering all this information, they will get the results: an estimate of the number of people who will avoid infection by using masks as a measure to prevent the spread of the virus. Graphs showing these results are presented below the calculator.

If 50 percent of the public wore face masks, the R0 value would drop to 0.9. To stop the epidemic, the R0 value would have to be lower than 1.

The authors of the tool point out that their calculator estimates very complex relationships in a simplified manner. For example, it does not take into account how quarantine affects the spread of the virus.

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