Given that testing has been severely bottlenecked from the start, are we sure the reported number of new deaths each day has been an (approximately) accurate count of all the COVID-19 deaths for that specific day? Stated another way, are we sure we haven’t been missing a lot of deaths on some days, or that deaths from multiple days aren’t being processed together as we work through backlogs of samples? When comparing the total number of tests vs. the total number of deaths over time, it’s a very tight linear relationship in both the U.S. and Italy (Python code for plot here):

so the two quantities must be increasing at close to the same rate in each country, respectively (specifically, the average daily growth rates are about 1.1 in Italy and 1.3 in the U.S. over the past two weeks). When two quantities are increasing at different rates, you see an exponential or logarithmic trend (because one is growing exponentially faster than the other). For example, if the number of tests in a hypothetical country was growing at Italy’s rate, but the number of recorded deaths was growing at the U.S.’s rate, then this is what you would see:

I’m wondering if the fact that the number of deaths is increasing at the same rate as the number of tests in two different countries with different rates of increasing testing suggests the number of deaths might depend on the number of tests in a way that could bias an analysis.

Regarding the rate of hospitalizations, could you elaborate on why a growth in hospitalizations of those with flu-like symptoms implies a growth in COVID-19? You mentioned that patients are more likely to show up to emergency rooms as awareness surrounding COVID-19 grew, but this would apply to those experiencing non-COVID-19 flu-like symptoms as well, right? In the 2017–2018 flu season, 45 million people got sick with influenza-like illnesses, but only 1.8% (i.e., 810,000) of those individuals went to the hospital. If that percent went up to just 4.0% because people were worried, that would be an additional one million people heading to hospitals. The WHO declared COVID-19 a pandemic on March 11th. On March 12th, searches for “coronavirus” first peaked. March 12th is the 66th day after the first Monday of the year, which is when the first peak in hospitalizations occurs in the plot.