The simple answer, according to experts, is no. But as the United States considers its next moves, there are lessons to be learned from what happened in China and other countries where cases are declining.

Striking a balance with measures that are effective but not inordinate is critical, according to public health researchers who warn that extreme policies such as mandatory regionwide quarantines could run into ethical, legal and logistical problems, or even backfire.

Instead, ramping up testing capacity, quickly isolating sick or suspected patients and introducing policies that limit public gatherings or require working from home have proved effective in China, Hong Kong, Singapore and South Korea.

“China’s most effective measures can be undertaken without violating human rights,” said Thomas J. Bollyky, a senior fellow at the Council on Foreign Relations and director of its Global Health Program. Actions such as “suspending public transport, limiting public gatherings, preparing their health-care system, testing significant numbers. Those are all things we should be doing in the United States.”