Coronavirus’s Unchecked Spread Prompts About-Face on Masks (2)

Wearing face masks, which health officials in many countries previously discouraged outside hospitals, is gaining converts as the coronavirus spreads across the globe.

So far, U.S. and international health authorities have mostly relied on virus-fighting measures such as physical distancing, while recommending frequent hand-washing. Masks, they’ve said, may serve little purpose among untrained users and should be prioritized for sick people and those looking after them.

Yet evidence that the stealthy coronavirus can spread in people with no symptoms is forcing officials to consider broader protective measures to stem a pandemic that’s killed more than 54,000 people, crippled health systems ...