New COVID-19 cases are surging again in the U.S., with experts warning they could signal another growing wave of infections.

The country on Wednesday reported over 200,000 new cases, the highest since February, according to data from Johns Hopkins University. Federal health officials warned the situation could get even worse over the coming months.

In the last two weeks, new cases increased by 57 percent across the country, according to The New York Times' tracker. New cases rose in almost every state, with Maine being the only state to report a slight decline in the past two weeks.

Dr. Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention (CDC), noted a steady increase in COVID-19 cases in the past five weeks at a White House briefing with reporters on Wednesday.

Hospitalizations also are rising, up 19 percent in the past week, though they remain much lower than during the Omicron wave, she said.

The pandemic is now two and half years old, and the U.S. has seen five waves of COVID-19, with the later surges driven by mutated versions of the coronavirus.

A fifth wave occurred mainly in December and January, caused by the much more contagious Omicron variant.

Experts are worried the country now is seeing signs of a sixth wave, driven by Omicron subvariants.

A third of U.S. should be considering masks

Despite the recent rising numbers of COVID-19 infections and hospitalizations in the U.S., local officials have been reluctant to reintroduce mask mandates or any other form of restrictions, with one in three Americans now saying the pandemic is over, U.S. media reported.

Walensky called for masking and other infection precautions.

She said more than 32 percent of the country currently live in an area with medium or high COVID-19 community levels, including more than 9 percent in the highest level, where CDC recommends that masks and other mitigation efforts be used.

For an increasing number of areas, "we urge local leaders to encourage use of prevention strategies like masks in public indoor settings and increasing access to testing and treatment," she said. 

Health officials said they are concerned that waning immunity and relaxed mitigation measures across the country may contribute to a continued rise in infections and illnesses across the country. They encouraged people, particularly older adults, to get boosters.

Some health experts say the government should be taking clearer and bolder steps.

The CDC community level guidelines are confusing to the public, and don't give a clear picture of how much virus transmission is occurring in a community, said Dr. Lakshmi Ganapathi, an infectious disease specialist at Harvard University.

When the government officials make recommendations but do not set rules, "it ultimately rests on every single individual picking and choosing the public health that works for them. But that's not what is effective. If you're talking about stemming hospitalizations and even deaths, all of these interventions work better when people do it collectively," she said. 

White House's warning on COVID-19 funding

Last week, White House COVID-19 coordinator Dr. Ashish Jha warned the U.S. will be increasingly vulnerable to the coronavirus this fall and winter if Congress doesn't swiftly approve new funding for more vaccines and treatments.

Jha warned that without additional funding, the virus would cause "unnecessary loss of life" in the fall and winter, when the U.S. runs out of treatments.

He added the U.S. was already falling behind other nations in securing supplies of the next generation of COVID-19 vaccines and the domestic manufacturing base of at-home tests is already drying up as demand drops off.

Jha said domestic test manufacturers have started shuttering lines and laying off workers, and in the coming weeks will begin to sell off equipment and prepare to exit the business of producing tests entirely unless the U.S. government has money to purchase more tests, like the hundreds of millions it has sent out for free to requesting households this year.

That would leave the U.S. reliant on other countries for testing supplies, risking shortages during a surge, Jha warned. About 8.5 million households placed orders for the latest tranche of eight free tests since ordering opened on Monday, Jha added. 

(With input from AP)