According to the New York Times,

The new data is partial and most likely undercounts the recent death toll significantly. But it still illustrates how the coronavirus is causing a surge in deaths in the places it has struck, probably killing more people than the reported statistics capture. These increases belie arguments that the virus is only killing people who would have died anyway from other causes. Instead, the virus has brought a pattern of deaths unlike anything seen in recent years.

A side note: You’ll recall a similar increase in previously unreported cases of coronavirus deaths in China from a couple of weeks ago. Those reports were met by many Americans with howls of protest and accusations of a coverup. I doubt we’ll hear those same accusations now, even though the circumstances that caused the increased numbers there match what’s going on here.