(NewsNation) — The U.S. Centers for Disease Control and Prevention issued a warning as COVID-19 cases and hospitalizations are on the rise across the nation.

New CDC data shows an increase in the seven-day moving average in new cases since late March. And a total of 40 states and Washington, D.C., are also now reporting a rise in hospitalizations, according to Becker’s Hospital Review.

If the number of COVID cases continues to go up, we could soon start seeing people standing in long lines at testing sites all over again.

There’s no need for panic, but it’s time to prepare, according to a message from public health officials as a sub-variant of the highly contagious omicron variant sweeps the nation.

Counties in Nevada, Nebraska and upstate New York are dealing with the most elevated COVID cases.

In Nevada, a state of 3.2 million people, there are 239 new cases per day. In Nebraska, according to the CDC, new cases have spiked 500% and in New York State with 19 million people, 12 died from COVID last Friday. Other states are worried their numbers will substantially increase in the coming days.

“This uptick in the numbers is, you know, makes us nervous about how far this is gonna go,” said Dr. Hasaan Khouli of the Cleveland Clinic.

In the northeast, New York, New Jersey and across New England, new COVID cases are among the highest in the country.

New York City raised its COVID alert level from low to medium and New York Gov. Kathy Hochul announced she tested positive for COVID.

“Thankfully, I’m vaccinated and boosted, and I’m asymptomatic,” Hochul, 63, tweeted. “A reminder to all New Yorkers: get vaccinated and boosted, get tested, and stay home if you don’t feel well.”

On the West Coast in Los Angeles County, there is a near 200% spike in new cases.

“We’re now into our sixth wave,” health officials said pointing to the relaxation of mask mandates and people socializing more closely as the reasons why COVID cases are spiking.

It was the omicron variant BA.1 that led to a surge of COVID cases over the winter. Now it appears the variant BA.2 is circulating heavily in the U.S. and scientists have identified at least three other sub-variants present around the world, each one more contagious than the next.

Last week, U.S. health officials restated their recommendation that Americans wear masks on planes, trains and buses, despite a court ruling last month that struck down a national mask mandate on public transportation.

The CDC estimates more than 5,000 people could potentially die from COVID in the coming weeks as the U.S. death toll from the COVID-19 pandemic approaches a 1 million milestone.

The Associated Press contributed to this report.