If the coronavirus isn’t contained, a severe global recession is almost certain

The world woke up Monday to the reality that the coronavirus epidemic is going to have a much bigger impact on the global economy than investors and policy makers had assumed. Just how big, no one really knows.

Last week, it seemed as if financial markets believed that COVID-19 would be contained. But new cases in Italy, South Korea and Iran over the weekend undermined that belief. The World Health Organization tried to reassure the public on Monday, saying the disease was not yet a pandemic because it was not...