The coronavirus shutdown is hammering supply and demand across the globe. That has forced the real economy into a sharp recession and triggered a rolling financial crisis. Below is a primer on one key piece of this mess: the crisis in corporate debt markets. This branch of finance is vitally important because even healthy companies often need access to credit. If they do not get it, they go under.

In 2008, the vector of crisis ran from mortgage-backed securities to the rest of the financial sector and then to the real economy. This time, the real economy is being hit directly, and the damage is reverberating back into financial markets.  The failing markets, in feedback-loop fashion, further threaten the real economy as corporations find it harder to borrow. As the corporate debt markets sour, major companies will go bankrupt. Unemployment is skyrocketing. Some analysts expect the economy to contract by an annualized rate of 30 percent during the second quarter of 2020.

Already, US financial markets are on public life support. The Federal Reserve has committed to unlimited purchases of all sorts of assets: US Treasuries, mortgage-backed securities, car loans, municipal debts, and, in a historic step, both short term and long-term corporate debt. But the crisis will require more than a financial rescue.