Covid Is Spreading in Unexplained Ways, Dimming Containment Hope

As countries across Asia Pacific struggle with resurgences of the coronavirus, one data point is steering government responses: the share of cases with no clear indication of how infection occurred.

These patients cannot be linked to other confirmed infections or existing outbreaks by virus responders, indicating hidden chains of transmission. A growing proportion of such cases in a city’s resurgence pushes governments, like in Australia and Hong Kong, to take broad and blunt action, returning entire cities to lockdown-like conditions.

How Do People Catch Covid-19? Here’s What Experts Say: QuickTake

“You can hardly contain the outbreak because you have no ...