The simple answer to what we don’t know about COVID-19 is just about everything. The Johns Hopkins Tracker that everyone is following presents a lot of data, most of which is uninterpretable. Let’s start with the number of cases. The Total Confirmed is not really that, rather it’s the number of patients with a positive test. A positive test may be a true positive or a false positive. All medical tests have a percent of positives that are false.
To be able to distinguish between the two you must know the sensitivity of the test used and the prevalence of the disease among those tested. Currently, we don’t know either. All you can be sure is that the number of infected patients listed under the heading Total Confirmed is less than the number given. The same overestimate is true for the number of cases given by country, state, or locality. These numbers are just those who tested positive – again an unknown mix of true and false positives.
Next Total Deaths. This too is an overestimate as it includes those who died from COVID-19 and those who died with it; it just counts patients who tested positive and subsequently died. Whether the virus had any effect on these deaths is not known.
The only number that is likely accurate is The Total Tested in the US. All that’s needed here is the ability to count. The problem with the Hopkins website is that it presents a worse than worst case scenario. I cannot overemphasize that there is a difference between a positive medical test and a true positive test. A failure to make this distinction can lead to dire results. Consider the meat processing plants that are closing because some of their workers have tested positive for the virus. The number of true positives is unknown, but the subsequent fear is 100%. This failure of analysis could put the US food chain in jeopardy.
No one I know of in the press or medical community is discussing the problems I just presented above. If we don’t sharpen our analysis of the data about this epidemic we will make its deleterious effects worse.