The CDC put the ratio of infections to confirmed cases in South Florida at 11 to 1, which is the same as the ratio it estimated in Utah, where the samples were collected from April 20 through May 3, and in western Washington, where the samples were collected from March 23 through April 1. Connecticut, where the blood was drawn from April 26 through May 3, had the lowest ratio of estimated infections to confirmed cases: 6 to 1. Missouri, where samples were collected from April 20 through April 26, had the highest ratio: 24 to 1.

What do these findings imply about the infection fatality rate (IFR) in these places? New York City had recorded 2,580 COVID-19 deaths as of April 1, when the CDC estimates 641,800 residents had been infected, which implies an IFR of 0.4 percent. (The IFR implied by the state health department’s study, by contrast, was around 0.6 percent.) The COVID-19 death toll in Connecticut was 2,495 as of May 3, when the CDC estimates the state had 176,700 infections. That implies a much higher IFR: 1.4 percent.

Utah had recorded 57 COVID-19 deaths as of May 3, when the CDC estimates the state had 47,400 infections, implying an IFR of just 0.1 percent. Missouri’s death toll was 388 as of April 26, when the state had an estimated 161,900 infections. That implies an IFR of about 0.2 percent.