The Centers for Disease Control and Prevention is conflating the results of two different types of coronavirus tests, distorting several important metrics and providing the country with an inaccurate picture of the state of the pandemic. We've learned that the CDC is making, at best, a debilitating mistake: combining test results that diagnose current coronavirus infections with test results that measure whether someone has ever had the virus. The agency confirmed to The Atlantic on Wednesday that it is mixing the results of viral and antibody tests, even though the two tests reveal different information and are used for different reasons. This is not merely a technical error. The upshot is that the government's disease-fighting agency is overstating the country's ability to test people who are sick with COVID-19. States have set quantitative guidelines for reopening their economies based on these flawed data points. Several states - including Pennsylvania, the site of one of the country's largest outbreaks, as well as Texas, Georgia, and Vermont - are blending the data in the same way. Virginia likewise mixed viral and antibody test results until last week, but it reversed course and the governor apologized for the practice. These results damage the public's ability to understand what is happening in any one state. On a national scale, they call the strength of America's response to the coronavirus into question. The number of tests conducted nationwide each day has more than doubled in the past month. At the same time, the portion of tests coming back positive has plummeted.