Mark Zandi is chief economist of Moody's Analytics. He was an advisor to John McCain's 2008 presidential campaign and supported Hillary Clinton in the 2016 presidential election. The opinions expressed in this commentary are his own.

The coronavirus is an existential threat to our record-long economic expansion. The Centers for Disease Control and Prevention (CDC) says it is likely that COVID-19 will become a global pandemic. If the CDC's warning comes to pass, then recession will be difficult to avoid.

This is also the assessment of global investors, who have dumped stocks in recent days as they vastly marked up the probability of a downturn. The stock market was overvalued and thus vulnerable to any turn of events that didn't stick to script. The downdraft in stocks — about 11.5% — has wiped out an astounding $3.4 trillion in stockholder wealth.

China's experience provides a good case study on how COVID-19 could wreak havoc on our own economy. Travel, tourism and trade will be significantly disrupted, if not shut down. The airlines and hotel chains are already grappling with cancellations. Workers won't be able to get to their jobs if they are sick or quarantined, and if schools and daycare centers close, parents will have to stay home with their children and work fewer hours.

Without workers, businesses will produce less, and workers who aren't working will buy less. This adds up to lower profits — or even losses. And that is what has stock investors particularly nervous. Most businesses will have little choice but to be more cautious and hold the line on investments and hiring. The hardest hit will have no choice but to lay off workers.

Worse, businesses were already on edge before COVID-19 showed up in China. The trade war between the United States and China has been especially disconcerting. It did significant damage to the global economy. Here at home, it has basically pushed the manufacturing agriculture and transportation industries into recession. President Trump signed a "phase one" trade deal with the Chinese earlier this year, just in time to avoid a full-blown downturn, but businesses remain uneasy. They figure the president will double down on his trade war if re-elected.

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