Every one of California's 40 million residents is now required to stay at home indefinitely following an order from Gov. Gavin Newsom that took effect Thursday night at midnight. The order -- one of the first statewide bans on going out in public, with few exceptions -- is aimed at arresting the spread of the coronavirus pandemic.

Efforts to control the deadly illness have ground the global economy to a halt in recent weeks, but those efforts have not kept the spread of COVID-19 from overwhelming healthcare systems in some parts of the world. 

Family at home.

Image source: Getty Images.

An effort to protect those most at risk and prevent hospitals from being overrun

Only hours before the order was made, California officials warned that the state was on a path that could result in more than half of its residents contracting COVID-19 and potentially tens of thousands dying. With hospitals and other medical facilities facing a scenario of far more patients than they could possibly care for, the risk of people dying simply because there would be no capacity to treat them played a major factor in Newsom's decision.

With few exceptions -- including visits to buy food, medicine, fuel, or other necessities, and to travel to and from work -- California residents are expected to stay home and to continue practicing social distancing when out in public. The hope is that these major restrictions will significantly slow the spread, buying the state's healthcare system breathing room as providers try to manage the patient load and acquire necessary supplies and equipment to deal with what is still expected to be a big increase in the number of patients.

After spending the early part of Friday moving higher, markets are falling sharply again in afternoon trading. At this writing, the SPDR S&P 500 ETF Trust (NYSEMKT:SPY) and SPDR Dow Jones Industrial Average ETF (NYSEMKT:DIA) are both down 4%, and they have fallen by roughly one-third since Feb. 19. This has been the second-fastest 30% decline in U.S. stock markets in the past 50 years.