WHY ASIA'S NEW WAVE OF VIRUS CASES SHOULD WORRY THE WORLD.

After a surge in cases tied to international travelers, China, Hong Kong, Singapore and other places that seemed to have the epidemic under control have imposed stricter measures. In China, international flights have been cut back so severely that Chinese students abroad wonder when they will be able to get home. In Singapore, recently returned citizens must share their phones' location data with the authorities each day to prove they are sticking to government-ordered quarantines. In Taiwan, a man who had traveled to Southeast Asia was fined $33,000 for sneaking out to a club when he was supposed to be on lockdown in his home.

In Hong Kong, a 13-year-old girl, who was spotted out at a restaurant wearing a tracking bracelet to monitor those in quarantine, was followed, filmed and subsequently shamed online. Across Asia, countries and cities that seemed to have brought the coronavirus epidemic under control are suddenly tightening their borders and imposing stricter containment measures, fearful about a wave of new infections imported from elsewhere. The moves portend a worrisome sign for the United States, Europe and the rest of the world still battling a surging outbreak: Any country's...