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In his post, epidemiologist Gikas Majorkinis explains the reasons why he is not convinced that class size is so important in the transmission of the coronavirus.
Majorkinis returns to the subject since his relevant report in yesterday’s briefing on the evolution of the pandemic provoked reactions mainly from users of social networks.
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“I understand that the intention is always the best of students and teachers but personally I think the answer is not that simple and I am not entirely sure that there would be (and if there was) a significant gain in reducing the transmission from 25 to 15 in terms of droplet transmission, “observes Mr. Majorkinis and tries, with the help of a diagram, to explain his position.
Gika Majorkinis’s post
After yesterday’s briefing at the Ministry, I go back to class size a bit because the discussion seems to focus there and I explain why I am not convinced it is that important.
The 1.5 meter distance is important for droplet transmission and should be observed as closely as possible in general. Where we cannot find a way to reduce the probability of transmission using a mask.
The same logic applies to schools with widespread use of masks in the classroom. It should be noted that classes cannot be considered dining areas. In focus there is a constant alternation of people gathered. Classes always have the same composition, so we can consider them as social “bubbles” or “bubbles”, so the logic in dealing with them is quite different. In principle, any transmission in the classroom is fully traceable and can be limited by a simple restriction, while focused creates “orphan” cases.
A constantly debated issue is: what is the load of distances> 1.5 meters in the classes of 25 students compared to the class of 15 students?
To help explain a bit, I have made a table of classes of 15 students (right). With green arrows I show the 2 distances of the student in the first desk with all the students in the next row (8 distances), for convenience I do not show the rest with students in the same series (6 distances). This student’s distances are 14 and they all exceed 1.5 meters. The total distances in this arrangement are 120.
As shown below, a class of 25 students, every 2 distances, is 325 to 13 to exceed the limit of 1.5 meters, that is, only 4% of all possible combinations. These “infractions” are only in the horizontal plane and do not allow transmission to the vertical axis of the order.
Therefore, from these calculations, converting the class to a size of 15 people eliminates 4% of every 2 distances during the lesson. At the same time, the number of teaching hours to be covered by teachers increases (almost doubles).
So, the scenario shows that for the possibility of transmission exclusively during the educational process in order to lower 4% of the close contacts, you will have to double the exposure time of the teachers.
I understand that intention is always the best of students and teachers, but personally I think the answer is not that simple and I am not entirely sure that there would be (and if there was) a significant gain in reducing the transmission from 25 to 15 in terms of droplet transmission.
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