When China’s Communist Party locked down an entire city to fight the outbreak of a new coronavirus there, some global public-health officials warned that the iron-fisted approach ignored world-wide norms for responding to epidemics and could make things worse.

Now, with the number of new cases across China dwindling—and rising outside its borders—the nation’s hard-line response to the pathogen is challenging decades of conventional wisdom about how best to handle infectious diseases.

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