evidence: Redfield is convinced that, had C.D.C. specialists visited China in early January, they would have learned exactly what the world was facing. The new pathogen was a coronavirus, and as such it was thought to be only modestly contagious, like its cousin the SARS virus. This assumption was wrong. The virus in Wuhan turned out to be far more infectious, and it spread largely by asymptomatic transmission. "That whole idea that you were going to diagnose cases based on symptoms, isolate them, and contact-trace around them was not going to work," Redfield told me recently. "You’re going to be missing fifty per cent of the cases. We didn’t appreciate that until late February." The first mistake had been made, and the second was soon to happen.