Health officials are warning that COVID-19 cases are on the rise, and could start surging during the fall and winter if people don't change their behavior.

New numbers from Johns Hopkins show more than 56,000 coronavirus cases were reported in the U.S. this week – the highest daily increase since mid-August.

Earlier this week, Dr. Deborah Birx, from the White House Coronavirus Task Force, toured the Northeast and stopped at Stony Brook University.

She said that there could be an early asymptomatic, silent spread happening now, likely the result of people gathering without masks in their homes or at social events.

Hot spots have already recently been popping up on Long Island.

As News 12 has reported, the state has identified coronavirus clusters in Brooklyn and Queens — labeled as the "red zone."

Some parts of Inwood and Lawrence, in southeast Nassau County, are in the orange zone. Neighboring Cedarhurst is in the yellow zone.

Dr. Anthony Fauci had a sobering warning for Americans earlier this week — that there could be as many as 400,000 U.S. deaths from coronavirus through the winter if behaviors don't change.

"The models tell us that if we do not do the kinds of things that we're talking about in the cold of the fall and the winter, we could have from 300,000 to 400,000 deaths," he said. "That would be just so tragic if that happens."

Dr. David Battinelli, of Northwell Health, says this should serve as a wakeup call about how easily coronavirus can spread.

"It's clear that people are not paying attention like they were a little while ago," he says. "If one case goes to two, two to four, four to eight, this doubling thing can happen very quickly and it can get out of hand very quickly. So, people need to be very careful."

So far, over than 213,000 Americans have died from COVID-19.