Recently, I’ve gotten some questions on news reports that the Centers for Disease Control and Prevention (CDC) and many states have been conflating two different types of COVID-19 tests in their reporting. The substance of both the news reports and the subsequent questions was that this conflation made the data unreliable and that the situation could be worse—with respect to the virus and the pandemic—than we had thought. Indeed, it is a reasonable concern. And given that I use various coronavirus data here on the blog, I thought it would be worth writing about what we know about the virus and how we know it.


