On a Jan. 15 conference call, a leading scientist at the federal Centers for Disease Control and Prevention assured local and state public health officials from across the nation that there would soon be a test to detect a mysterious virus spreading from China. Stephen Lindstrom told them the threat was remote and they may not need the test his team was developing "unless the scope gets much larger than we anticipate," according to an email summarizing the call. "We're in good hands," a public health official who participated in the call wrote in the email to colleagues. Three weeks...