Thanks for your editorial on March 24 addressing our local virus problem — leading the nation. I was wondering why Idaho Falls and Bonneville County have seen a high surge in cases while many people in the supposedly most-endangered groups have been vaccinated. I suspect that the most-endangered now are people in Idaho Falls who do not wear effective masks and do not physically distance themselves from other people (infected carriers) adequately.

Anyhow, I want to quibble with your recommendation to use surgical masks for protection against the virus. In the Guardian on March 11, Christina Jewett belatedly pointed out that surgical masks apparently are ineffective at filtering the aerosol particles that carry the virus. This situation was known already early last April in Bavaria and Austria from experiments at University der Bundeswehr near Munich by professor C. J. Kaehler and Rainer Hain; the results were published in J. Aerosol Science, online since June 28, 2020.

A demonstration by professor Kaehler showing the failure of surgical masks to filter appropriate aerosol particles is available at youtu.be/835UQQdKMm4. And, as you suggest, KN95 and N95 masks are effective at removing most of the virus particles. Having had both vaccinations, I still plan to wear my KN95 mask and avoid people.

D. M. McEligot

Idaho Falls