Surgeon General Jerome Adams said U.S. citizens need to prepare themselves for an excruciating week of coronavirus deaths.

“This is going to be the hardest and the saddest week of most American's lives, quite frankly. This is going to be our Pearl Harbor moment, our 9/11 moment; only it’s not going to be localized. It’s going to be happening all over the country. And I want America to understand that,” Adams told Fox News Sunday.

As of Tuesday, the coronavirus had killed more people in the United States than 9/11, the deadliest terror attack in the country’s history.

He said an aggressive response, such as practicing social distancing and staying home, could change the trajectory of the pandemic. The Centers for Disease Control and Prevention has also recommended that all citizens wear cloth face masks when in public.

“I want Americans to understand that, as hard as this week is going to be, there is a light at the end of the tunnel if everyone does their part for the next 30 days,” he said.

The U.S. has more than 312,000 confirmed cases of the coronavirus as of Sunday morning, according to a Johns Hopkins University tracker. More than 8,500 people have died from the virus, and at least 15,000 people have recovered.