Ongoing fears of economic fallout from the COVID-19 outbreak mixed with falling oil prices sent stocks plunging Monday, causing the markets to halt trading early in the morning. The spreading disease has led to Wall Street’s weakest performances since the 2008 financial crisis.

To explain what happened, Megan Greene, economist and senior fellow at Harvard University, spoke with “Marketplace” host Kai Ryssdal about the acceleration of the illness and its impact on global supply and demand. They also discussed how these events could play out long term.

“It depends entirely on epidemiology,” Greene said. “And none of us really have answers there. So it really depends on how far this virus spreads.”

Click the audio player above to hear the interview.