How interesting!
FWIW, this website says the advice has been debunked.
My email from medicare.gov:
Take preventive action now against COVID-19
According to the CDC, older adults and people who have severe chronic medical conditions like heart, lung or kidney disease are at a higher risk of serious illness if they contract the COVID-19 virus. This means that most people with Medicare are at a higher risk.
Your health, safety, and welfare is our highest priority. In addition to practicing good everyday prevention through things such as hand washing and avoiding touching your face, the CDC says there is more you can do to take precautions against COVID-19 and reduce your risk of exposure:
Avoid crowds, especially in poorly ventilated spaces with limited air circulation.
Defer all cruise ship travel worldwide, particularly if you also have underlying health issues.
Avoid situations that put you at increased risk, including non-essential travel such as long plane trips.
I do that every morning and the windows are open.