I can absolutely believe this, and I'll tell you why.
As most of you know by now, I'm a Hutterite. We are sort of the perfect test case for the spreading of germs. We eat communally three times daily (buffet style), we sit just a few feet apart in church, and when it comes to the children, there literally is no separation at any time.
Now, when schools closed on March 23, we all started eating at home, one person from each family went to get food, and this was coordinated so that we had low numbers of people in the kitchen at any given time. School was online / home school and church was over the public address system. People from other communities could not visit us, and vice versa.
During March and April, which tend to still be prime cold and flu season due to weather and temperature variations - can you guess what happened? I'm sure you can - colds and flus were (and still are) drastically reduced, almost non - existent.
We probably won't be able to maintain these practices indefinitely, but some of them will certainly stay in place.