Just how deadly is Covid-19 compared with the flu, which kills about 0.16% of its victims (including 125 children so far this season)? On Tuesday, the World Health Organization’s Bruce Aylward, having returned from a painstakingly negotiated visit to Wuhan, seemed to argue for accepting the Chinese figure of roughly 2%. But remember Stalin’s quip about the pope’s army: The WHO is dependent on China’s goodwill, has little power to coerce China, and understands how readily Beijing might cut off cooperation in a fit of neo-Maoism.

Mr. Aylward’s view is strongly disputed by many other experts. In the chaos of Wuhan, they suspect China missed thousands of mild cases while also letting dozens die who would have lived with proper advice and care. Numerous have been the press reports of elderly victims expiring at home after being turned away from hospitals.

Here’s my guess (and it’s just a guess): Once authorities in the U.S. start looking seriously for domestic Covid-19, they are bound to find it. The pillorying of California for not detecting its case sooner is really just evidence of how slow the media has been to grasp the Covid-19 challenge. Which of the million-plus people who come down with flu symptoms each week should be given the expensive, hard-to-obtain test? Which of the thousands who check into hospitals with generic breathing difficulties?