From an interview with "Nobel laureate Michael Levitt, an American-British-Israeli biophysicist who teaches structural biology at Stanford University":
"In exponential growth models, you assume that new people can be infected every day, because you keep meeting new people. But, if you consider your own social circle, you basically meet the same people every day. You can meet new people on public transportation, for example; but even on the bus, after some time most passengers will either be infected or immune."
Another reason the infection rate has slowed has to do with the physical distance guidelines. "You don't hug every person you meet on the street now, and you'll avoid meeting face to face with someone that has a cold, like we did," Levitt said. "The more you adhere, the more you can keep infection in check. So, under these circumstances, a carrier will only infect 1.5 people every three days and the rate will keep going down."
As for Italy:
the explosion of cases in Italy is worrying, Levitt said, but he estimates it is a result of a higher percentage of elderly people than in China, France, or Spain. "Furthermore, Italian culture is very warm, and Italians have a very rich social life. For these reasons, it is important to keep people apart and prevent sick people from coming into contact with healthy people."
And from Richard Epstein's latest column, which is worth reading in full: "I believe that the current dire models radically overestimate the ultimate death toll....In light of the available raw data, public officials have gone overboard."
Neither Levitt nor Epstein is a medical doctor. I would emphatically caution readers to follow the advice being given by federal, state, and local authorities about washing hands frequently and keeping six feet away from other people. The medical doctors I do know are concerned about the risk of the hospitals being overwhelmed. But the panic that has taken hold in the financial markets and in some policy circles is so great that we are nearing the point at which a surprise on the positive side — a better-than-expected outcome — is worth considering in addition to the terrible outcome that everyone seems to be expecting. This is not about "optimism" or "pessimism" or "wishful thinking" or pretending that the public health threat does not exist. But it's easy to be misled by soaring case numbers: they may indicate increased testing availability rather than increased spread of the disease. (As Nate Silver put it on Twitter, "Something like 'known or presumed coronavirus-related ICU admissions' would be a more reliable indicator of the actual rate of growth.")
One way for government officials to reassure the public would be to provide a public count of critical-care hospital beds available in a state or city or county versus critical-care hospital beds currently occupied. If there's plenty of remaining capacity, let people know that. Not so that people can immediately go back to bars and gyms and stop washing their hands, but so that some of the crippling anxiety is eased. That would get us closer to some middle ground between the two extreme alternatives of doing nothing to slow the pandemic's spread and shutting down the world economy indefinitely.