12 Augustus Masks

Wed, 08/12/2020 - 21:18

Dear colleagues,


As you know, I try to keep a “detached” scientific position, high and dry in my study room at the outskirt of the pleasant city of Lier (Lierke plezierke).  “Au dessus de la mêlée” as they say in French. But sometimes,  ....


I have been convinced that wearing a quality mouth/nose cap (I don’t like “masks”) can help us through the various COVID-waves, until we find a more sustainable solution (like a vaccine).

But it is difficult to prove that it really works, because a standard “double blind placebo-controlled” trial is impossible to set up. Most evidence until now is “circumstantial”, leaving always room for disbelief and alternative explanations.

Not sure how many of you still need to be convinced, but here are some good recent lab studies and epidemiological evidence for the “unbelieving Thomas’s”  amongst you (if there are any remaining)


The first study on 14 types of masks (Fig 2 p. 7 and Table 1 p. 8)  clearly shows how microdroplets from regular speech are retained.  Not unexpectedly, the N95 (FFP2) and 3layer surgical masks are superior, followed by multilayered fabrics.  Single layered fabrics and knitted masks behave poorly, but “Bandanas” and “Fleeces” are even worse than nothing!  Remember that Koen Geens  (Law professor, Minister of Justice and Governmental Mask Deliverer see last attachment) advised us to wear bandanas, while waiting for the “real stuff”    


The second paper is probably even more practical: it shows that the filtration efficiencies of the hybrids (such as cotton-silk, cotton-chiffon, cotton-flannel) was very high and even better thzan N95 (Fig 3A p.5).  It also shows how leaving gaps (as many people do) dramatically decreases efficiency.  Not unexpected, but here is the measured evidence…


The third paper is a meta-analysis that evaluates the efficacy of distancing, face masks and eye protection.   Just like you cannot doubt about distancing, it becomes very hard to keep on saying that the efficacy of masks is “not clear”….


Finally a more speculative paper, arguing that the population-based masking not only prevents viral spread from infected people, but also prevents infection, or at least reduces the inoculum in such a way that infected subjects are more likely to be asymptomatic.  They argue this point by comparing cruise ships where masking was applied early and consistently versus late and by comparing countries with universal masking (Far East and Tchec republic) versus those were it was not or only late adopted (most of Europe and US). 


Finally, for those who read Dutch, a plea from our coleagy Detlef Lohse (Twente University) in a regular newspaper: https://www.ad.nl/binnenland/onderzoek-wijst-uit-mondkapjes-in-kroeg-absoluut-noodzakelijk~a74e43c7/?referrer=https://www.google.com/

…while Mr Rutte is still a non-believer and the second Dutch wave is hitting The Low Lands by the Sea…..


On the other hand, sometimes there is overshooting.  I live close to a natural reserve “De Kesselse Heide”, which during the week, is nice and quiet for a lonely walk.  But since two weeks I should wear a mouth/nose cap there, even if I am alone with the crickets and the mosquitoes….

And, then, if next I go into a busy place in town, wearing a single layer paper cap, a fleece or anything else over my nose and mouth, nobody will make a remark, since I’m a good citizen….  


I do think there is need for us medics to join with material scientists, come up with very concrete advice on which caps have a good price/quality, how you should wear and treat then and then give consistent, repeated and reasonable messages to the population on whom, where, when and how to use mouth/nose caps. And please don’t change your mind, each time the level of infection goes slightly up or down: the virus will stay with us for a while and there is no good reason to get infected. But even the most patient and obedient people get so confused, angry and/or anxious when the rules are unclear and change all the time.   


Hope you  are still with me…. 


If not, don’t worry: I will return to less controversial scientific topics….