Because our random sample was designed to be representative of the population of the state, we can assume with almost certainty that the entire state numbers are the same. That would mean that approximately 188,000 Indiana residents had been infected by late April. At that point, the official confirmed cases—not including deaths – were about 17,000.
Focusing the tests on severe or high-risk people underestimated the true infection rate by a factor of 11.
Having a reliable estimate of the true number of people who have been infected also allowed us to calculate the infection fatality rate—the percentage of people infected with SARS-CoV-2 who die. In Indiana, we calculated the rate is 0.58%. For this calculation, we divided the number of COVID-19 deaths in Indiana—1,099 at the time—into the total number of people that were determined to have been cumulatively infected at 2.8% of the population—188,000.
Early estimates suggested that 5% to 6% of cases in the U.S. were fatal, which is similar to the 6.3% that you would get by dividing confirmed cases in Indiana—17,000—by the deaths—1,099. The infection–fatality rate of 0.58% is thankfully far lower, but is nearly six times higher than the seasonal flu which has a death rate of 0.1%.
This random testing also allowed us to make accurate estimates about what percent of infected people are asymptomatic. In our study, about 44% of those who tested positive for active viral infection reported no symptoms. While this was already suspected by experts, our estimate is likely the most accurate to date.
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Last edited by 360view; 07/22/2012:06 PM. Reason: 2nd weblink added
