(Bloomberg) --

The U.S. is moving in the “wrong direction” in combating a new wave of the Covid-19 pandemic accelerated by the delta variant as vaccinations slow, said Anthony Fauci, the nation’s top infectious disease expert.

With half of the country still not fully vaccinated, it’s a problem for the U.S., he said. Based on the modeling of data, the country faces a worst-case scenario of daily deaths reaching the winter peak of 4,000.

“I’m not sure if it’s going to be the worst-case scenario but it’s not going to be good,” he said on CNN’s “State of the Union.” “We’re going in the wrong direction. It’s like we have two kinds of America.”

Fauci also defended the decisions by Los Angeles and St. Louis to reimpose mask orders regardless of vaccination status. The local governments have the discretion to access and introduce rules that fit the situation on the ground, he said, adding that the cities’ action aren’t incompatible to what the Centers for Disease Control and Prevention is recommending.

Read: L.A.’s Mask Mandate Revives Old Divide as Virus Resurges

CDC Director Rochelle Walensky said July 22 that the organization was sticking with its recommendations that fully vaccinated people don’t usually need masks, while allowing that wearing one may have some advantages. That came as a number of public-health experts are urging the CDC to recommend that even fully vaccinated people wear face masks in public amid the resurgence of virus cases fed by the delta variant.

Read: As Delta Spread Quickens, CDC Pressured to Revise Mask Guidance

The U.S. had its worst week in three months as weekly cases surged fourfold from a month earlier with the spread of the highly contagious delta variant.

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