The S&P 500 was down 97.54 (3%) following Monday’s drop of 3.4%. The Dow Jones Industrials tacked a 879.51 (3.2%) loss onto yesterday’s 3.6% loss. The Nasdaq slipped an additional 255.67 (2.8%) after the previous 3.7% drop and the Russell 2000 fell 50.87 (3.1%), adding to the 2.9% retreat on Monday.

Today’s results were a double disappointment. Monday was bad enough with the Dow, S&P 500, and Russell 2000 losing all their gains for the year. Only the tech-heavy Nasdaq had kept any upside, which was cut to 2.8% since January. Today, that too is gone.

The second disappointment was that as of this morning, the market seemed to be eyeing a comeback. That turned once the Centers for Disease Control issued a warning against nonessential travel to China and South Korea amidst the spread of COVID-19, and an alert suggesting postponement of nonessential travel to Italy, Japan, and Iran.

“The CDC announcement today suggested that the problem is going to be prolonged,” said Tom Smythe, a professor of finance at Florida Gulf Coast University. That’s caused investors to shift money from equities into “safe havens” like government bonds. (The 10-year Treasury yield hit an historical intraday low of 1.317% today, which means there was heavy buying of the vehicle.)

Market watchers say two primary factors are at work here.

“The first, and most consequential, is when outbreaks are in areas central to manufacturing,” Kevin Philip, managing director of Bel Air Investment Advisors, wrote to Fortune. China, Japan, and South Korea are already feeling an impact, as is northern Italy, which is part of a major pan-European manufacturing hub.

The second risk is reduced economic activity. As Victor Carlström, chairman of investment firm Vinacossa Enterprises, told Fortune yesterday, “The only place where people act normal is in the U.S.” Many stores and malls across Asia are closed and consumer activity in Europe has already begun to feel pain. All economies depend on consumer spending.

“Many U.S. businesses that are deeply intertwined with the global economy—apparel, electronics, energy—are issuing warnings that their results are likely to be affected because of the virus,” said Raul Elizalde, president and chief investment officer of Path Financial, in a note to Fortune.

Some investment professionals are trying to see the bright side. “The hope is the market will view it as a onetime event and look past the inevitable decline in GDP and corporate earnings, but until we get a better idea of what the one time impact will be, markets will likely remain volatile,” Rob Edel, chief investment officer of Nicola Wealth wrote to Fortune.

But Elizalde thinks the situation may be different. “The only question is the extent of the damage, and that will depend on the duration and extent of the disease’s spread,” he said. “This is why the stock market’s weakness cannot be just dismissed as simple volatility. The effects on the real economy are very likely to be real.”

The challenge now for investors is to avoid full-out panic. “Although I know it is a little scary at the moment, try to keep your eyes focused on the long term,” said Stephen Auth, chief investment officer for equities at Federated Hermes, in a note to Fortune. “Markets are likely to be considerably higher further out, and the present worries, like many others we’ve been through before, will be just specks in the economic landscape.”

More must-read stories from Fortune:

—Europe’s first big Covid-19 outbreak roils global markets
—Billionaires are donating to fight China’s coronavirus
—94% of Fortune 1000 are seeing coronavirus supply chain disruptions
—Coronavirus misinformation is fueled by government mistrust
—Coronavirus may be the straw that breaks the back of oil fracking

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