The head of the US Centers for Disease Control and Prevention warned Tuesday that a second wave of the coronavirus pandemic expected this winter could be deadlier than the current pandemic.

“There’s a possibility that the assault of the virus on our nation next winter will actually be even more difficult than the one we just went through,” CDC Director Robert Redfield told the Washington Post, saying it would likely coincide with peak flu season.

“And when I’ve said this to others, they kind of put their head back, they don’t understand what I mean.”

Two simultaneous outbreaks of respiratory infections would dramatically strain the health care system, he said.

The first wave of COVID-19, the disease caused by the coronavirus, has already killed more than 42,000 Americans.

Redfield said federal and state officials need to use the coming months to prepare for a worst-case scenario.

As stay-at-home orders are lifted, officials need to stress the importance of social distancing and hand washing, he said.

Asked about protests against stay-at-home orders and some residents’ demands that states be “liberated” from restrictions — an effort President Trump backed on Twitter — Redfield declared: “It’s not helpful.”