People walk in Union Station's Main Hall in Washington, Monday, March 16, 2020. (Photo: AP) 

Millions of Americans began the work week holed up at home against the coronavirus Monday, worried not just about getting sick but about what the unprecedented near-shutdown of the US could do to their jobs and their savings.

With wide swaths of the economy shuddering to a halt, stocks nosedived more than 11% on Wall Street at one point in the morning, in a sell-off so fast that it triggered an automatic 15-minute halt to trading.

The best-case scenario for many investors now is that the economic shock will be steep but short, with growth recovering later this year as stores and businesses open back up. Pessimists, though, are preparing for a longer haul.

The US surgeon general, meanwhile, said the number of coronavirus cases in the United States has reached a level comparable to what disease-battered Italy recorded two weeks ago — a signal that infections are expected to rise in America.

“We are at a critical inflection point in this country, people,” US Surgeon General Dr. Jerome Adams told Fox News. “When you look at the projections, there’s every chance that we could be Italy.”