If you recall the advice from CDC and WHO since early 2020, you may notice that they strongly advised washing hands in the first few months, and did not emphasize wearing face masks as much, let alone social distancing. This is unfortunate misguidance to the public in view of the fact that the new coronavirus SARS-CoV-2 is air-borne and transmits more through people's breath and less through touching.[note1] I wish the experts at these organizations had emphasized wearing face masks and keeping social distance more than or at least as much as washing hands early on.
Anyway, to confirm my impression that the ratio of advice on wearing masks to hand washing increased in the past few months, I took advantage of Microsoft search engine Bing's historical searches.[note2] First I search on bing.com for "wash hands" (no quotation marks used) while limiting the time range to 1/1/2020 - 1/31/2020, 2/1/2020 - 2/29/2020, ..., 6/1/2020 - 6/30/2020. I record the approximate search result counts given by Bing. Then I search for "wear masks" and record the same counts. The result is in the following.
wash hands wear masks
1 524,000 362,000
2 643,000 557,000
3 2,220,000 1,640,000
4 2,090,000 3,620,000
5 2,490,000 5,350,000
6 2,270,000 4,860,000
The left column is the month, January (1) through June (6). The right column is the search result count for the month. We can tell that "wash hands" was found on much more webpages in March than February as if Americans woke up to the grim reality in March. So was "wear masks". But "wash hands" more or less reached a plateau, while "wear masks" overtook "wash hands" in April and stays in the lead ever since.
This comparison by no means is a direct proof of CDC or WHO's failure to advise the more efficient preventive measure, because the Bing-indexed webpages are authored by all sorts of people. But the public listens to these health authorities. If they say more about "wash hands" and less about "wear masks" and "social distancing", people do it, too.
By the way, the latest Economist magazine has an article Face-off over face-masks: Europe’s latest north-south split, which shows that more and more people in 14 countries started to wear face masks over time. It's interesting to see that Asian countries generally have a sharper rise of the curve than those in Americas and Europe, apparently reflecting the Asian tradition of collective compliance. (The reason China appears to be high all the time is that the data didn't start till February, when COVID-19 was already spread in China.)
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[note1] Not that touching contaminated surfaces is less risky. But the probability of touching such surfaces and bringing the viruses into the body is lower than directly receiving air-borne viruses in an environment where at least one person is virus carrier or spreader.
[note2] Google also provides historical search results. But in these searches, the estimated result counts are not given.
