First, they underestimate the rate of adaptive responses, which should slow down the replication rate. Second, the models seem to assume that the vulnerability of infection for the older population—from 70 upward—gives some clue as to the rate of spread over the general population, when it does not. Third, the models rest on a tacit but questionable assumption that the strength of the virus will remain constant throughout this period, when in fact its potency should be expected to decline over time, in part because of temperature increases.
As of March 16, the data from the United States falls short of justifying the draconian measures that are now being implemented. As of two days ago, 39 states have declared states of emergency, and they have been joined at the federal level with President Trump’s recent declaration to the same effect. These declarations are meant to endow governments with the power to impose quarantines and travel bans, close schools, restrict public gatherings, shut down major sporting events, stop public meetings, and close restaurants and bars. Private institutions are imposing similar restrictions. The one-two punch of public and private restrictions has caused a huge jolt to the economy.
The irony here is that even though self-help measures like avoiding crowded spaces make abundant sense, the massive public controls do not. In light of the available raw data, public officials have gone overboard.