Short version, SARS and MERs were way more deadly, so killed the host, which hurts transmission and virus survivability. The other key is that they were large droplet spread. We used those as our early basis for Covid-19, hence the early guidance on hand washing and 2 meters away etc. Also, masks are highly effective with large droplet spread. This is the article that really helped.
Transmissibility and transmission of respiratory viruses | Nature Reviews Microbiology
A study recently found that SARS-Cov-2 appears in higher concentrations in smaller water droplets rather than larger ones (85% small, 15% large).
Viral Load of SARS-CoV-2 in Respiratory Aerosols Emitted by COVID-19 Patients while Breathing, Talking, and Singing | Clinical Infectious Diseases | Oxford Academic (oup.com) The result being that while it certainly can be spread by droplets (somebody sneezes near you), that may not be the primary mode of transmission (although many older studies say it is). It's also why surfaces aren't significant (everyone now agrees). If this is correct, spread may be mostly by aerosols, which accumulate over time (for which cloth masks do less). It helps explain why people who work outside the house and live in smaller homes in dense areas have borne much of the pandemic. Air circulation, ventilation, filtration and of course, being outside, that does a lot. A study from Japan showed opening two windows once an hour dramatically reduced concentrations.
My suggestion would be to
end all the expensive cleaning activity, invest that Covid relief money immediately into air quality improvement in schools and all public buildings, including mass transit. Aircraft are already fine, which is why spread there is minimal. Private businesses should focus on the same, and perhaps relief funds can be targeted to that end. Unlike all the money we've wasted, those changes would have lasting impact and would reduce flu cases as well.
