ATLANTA, Ga. (CW69 News at 10)  — With half of the states reporting a rise in new cases, including Georgia, one expert warns of ‘danger signs’ in some parts of the United States.

On Saturday, Georgia saw its highest number of new confirmed cases since the pandemic began.  Yesterday was its sixth highest and three of the eight days where more than 1,000 cases were reported have occurred in the last week, according to the Johns Hopkins Coronavirus Resource Center.

After weeks of many Americans failing to heed face mask and social distancing guidelines, health officials in some states are reporting an increase in younger populations testing positive — saying those individuals are often asymptomatic but could be infecting others. And public health measures meant to control infection aren’t quite up to speed — a problem the country has consistently faced in past months.

“As you reopen … you expect to see more cases. But what we’re hearing, in terms of the public health model — of testing people, through contact tracing, and then isolation and quarantine — it doesn’t sound like it’s working as well as it really needs to,” says former acting director of the U.S. Centers for Disease Control and Prevention, Dr. Richard Besser.

Besser said Monday night he sees “some real danger signs for places like New York, New Jersey, Washington (DC).” New York City, Washington, DC, and the state of New Jersey have entered their second phase of reopening.

Others also point to Florida and Texas as other areas of concern. According to Florida’s health department, the state surpassed 100,000 total cases Monday and experts say it could be the next U.S. coronavirus epicenter.

In Texas, several mayors have raised concerns about the pace at which the state is reopening. Houston is “moving very fast in the wrong direction,” said Mayor Sylvester Turner after the city recorded a new high of daily coronavirus cases, according to CNN affiliate KTRK.

“This is a healthcare crisis,” he said. “And quite frankly, your failure, for example, to wear masks … or to engage in social distancing directly impacts on somebody else,” he said, according to the affiliate.

The trends in each state

At least 25 states are now recording a rise in new cases compared to last week, according to data from Johns Hopkins University. Those states are: Arizona, California, Colorado, Delaware, Florida, Georgia, Hawaii, Idaho, Kansas, Michigan, Mississippi, Missouri, Montana, Nevada, Ohio, Oklahoma, Oregon, South Carolina, Tennessee, Texas, Utah, Washington, West Virginia, Wisconsin and Wyoming.

In California, Los Angeles County recorded another single-day high in new cases, with 2,571 new confirmations.

The state recorded more than 35% of its total infections in the past two weeks.

Several sheriffs have said they won’t enforce an order issued by the governor that requires face masks in “high risk” settings, including any indoor public space and while taking public transportation.

“It is each person’s responsibility to wear a face covering, and follow other recommended safeguards, in order to stop the spread of Covid-19; it is not law enforcement’s responsibility to enforce it,” Orange County Sheriff Don Barnes said.

In Tulare County, the sheriff’s office said they “do not have the resources to conduct mask enforcement.”

States seeing steady, declining cases

States in which new cases are trekking steady are: Alaska, Arkansas, Illinois, Iowa, Kentucky, Minnesota, Nebraska, New Mexico, North Carolina, North Dakota, Pennsylvania and Virginia.

Meanwhile, cases are on the decline in Alabama, Connecticut, Indiana, Louisiana, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, South Dakota and Vermont.

As cases rise in other states, New York Gov. Andrew Cuomo said he may consider forcing visitors from high-transmission states to quarantine upon arrival.

U.S. still catching up to the virus

Some officials have blamed the increase in cases in more widespread testing. But experts say while testing is partly contributing, cases of the virus are also on the rise.

Even with the increased testing, one official says the U.S. is still not testing enough and is “way behind the virus.”

“We are still reacting. We’re not ahead of it,” Kathleen Sebelius, the former secretary of the U.S. Department of Health and Human Services, said Monday.

“The only way to get ahead of the virus is to tamp way down the cases in any area, and then test like crazy when a case appears, contact trace, and make sure you quarantine. We can’t do that yet because we are still finding all kinds of people who have the virus.”

And a new study now suggests as many as 8.7 million Americans had the virus in March — but more than 80% of them were never diagnosed.

The researchers behind the findings used data collected from each state by the CDC for influenza-like illness. The CDC uses this data to track the annual seasonal flu epidemic and asks doctors to report all cases of people coming in for treatment for fever, cough and other symptoms caused by influenza.

“We found a clear, anomalous surge in influenza-like illness (ILI) outpatients during the Covid-19 epidemic that correlated with the progression of the epidemic in multiple states across the US,” the researchers wrote.

The findings are further proof the virus has long been spreading under the radar and thousands of Americans could have at one point been infected — and passed the virus on to others — without ever knowing.

©2020 CBS Broadcasting Inc. All Rights Reserved. CNN contributed to the story.