Single coronavirus case exposes a bigger failure to track spread

The new Covid-19 case in a California woman with no travel history to China and no known contact with a person with the infection exposes a bigger problem: The virus is likely spreading undetected within the U.S., and experts still don't know how broadly the spread is. Before this new case was announced, the CDC had been reluctant to expand its testing protocol — only 445 people had been tested for the virus in the U.S., a fraction of the number in other countries. Even the woman in California, because she had no travel history, was initially refused a CDC test. It was only after she had been in the hospital for more than 10 days and her conditioned worsened did the CDC agree to have her tested. Now, the agency has changed its protocol, saying that those whose symptoms are consistent with Covid-19 and have a travel history to four other high-risk countries beyond China ought to be tested.