As China continues to reel from the spreading coronavirus, the world is looking for a familiar entity to swoop in and save the day: a central bank, in this case the People's Bank of China.

This time, though, even big rate cuts and other forms of easing may not be enough.

Central banks like the PBOC and its counterparts around the world — notably the U.S. Federal Reserve and the European Central Bank – have been bailing out economies and financial markets since the 2008 financial crisis. Trillions in digital money printing along with bargain-basement interest rates have been the main weapons of choice to combat recurring episodes of slowness.

On cue, the PBOC on Monday announced a massive reverse repo program — swapping high-quality securities for cash — along with corresponding cuts in short-term rates.

In the virus case, though, policymakers are facing a major unknown that comes at a time when China's economy already was slowing. This may be one instance, then, where opening the spigots on monetary policy isn't enough.

"We doubt that [the steps announced Monday] alone will be enough to put China's economy back on track," Hubert de Barochez, markets economist at Capital Economics, said in a note to clients. "The latest cuts will do nothing directly to offset the drag on economic activity from Chinese authorities' response to the epidemic – notably travel bans and business closures."

"And even in the most optimistic scenario – whereby the epidemic would be put under control rapidly and things would go back to normal soon – we think that the PBOC would need to cut rates again this year," he added.

That was a recurring theme as China's main stock index dropped nearly 8% Monday.