The actual number of people in the United States infected with the novel coronavirus could be over 20 million, nearly 10 times higher than what has been recorded, according to a new estimate from the US Centers for Disease Control and Prevention. On Thursday, some states paused reopening as the number of COVID-19 cases surge.

The estimate is based on serological testing used to determine the presence of antibodies that show whether an individual has had the disease. It comes as the government noticed many new asymptomatic COVID-19 cases showing up in young people who may not know they have it.

The estimate of 20 million infected with the coronavirus is about 6 percent of the US population and nearly 10 times as many infections as the 2.3 million confirmed cases in the country.

"It's clear that many individuals in this nation are still susceptible," Robert Redfield, CDC director, said during a call with reporters on Thursday. "Our best estimate right now is that for every case reported, there actually are 10 more infections."

Previously, White House adviser and top scientist Anthony Fauci and CDC officials have said that as many as 25 percent of infected people might not have symptoms. As of Thursday, the US had reported 2,374,282 confirmed COVID-19 cases and 121,809 deaths from the virus, according to the tally kept by the CDC.

Globally, there were nearly 9.3 million confirmed cases and nearly 480,000 deaths as of Friday morning, according to the World Health Organization.

Texas Governor Greg Abbott and Florida Governor Ron DeSantis on Thursday put a halt to any further reopening of businesses in their states as cases of the novel coronavirus surged.

Abbott also issued an executive order suspending elective surgery in four counties hit hard by an increase in COVID-19 hospitalizations. The counties are home to major cities: Houston, Dallas, San Antonio and the state capital, Austin. More than 4,300 people with the virus are hospitalized across the state, more than double the number at the beginning of June.

Abbott, a Republican, has said repeatedly that rolling back the state's reopening would be a last resort, and he repeated that on Thursday.

"The last thing we want to do as a state is go backwards and close down businesses," he said in a statement. "This temporary pause will help our state corral the spread until we can safely enter the next phase of opening our state for business."

He said that businesses already reopened can continue to operate and urged Texans to help contain the spread of the virus by washing their hands regularly, wearing masks and practicing social distancing.

Florida's DeSantis, who has repeatedly asserted that he didn't plan to stop the state's reopening, said, "We never anticipated necessarily doing anything different in terms of the next phase at this point anyways. We are where we are."

Florida reported 5,508 new COVID-19 cases on Wednesday, bringing the total to more than 114,000. Orange County, home to Orlando, is averaging 353 new cases a day, compared with 73 two weeks ago.

DeSantis, also a Republican, has pressed older people to stay home as much as possible. He has also pleaded with young people to be responsible, saying they account for the rising infection rate.

Since Wednesday, several states have mandated the use of face coverings in public, indoors and outdoors. They include Nevada, Washington and North Carolina, the first state in the South to do so.

North Carolina was supposed to move into phase three of its reopening plan on Friday, but Governor Roy Cooper, a Democrat, said on Wednesday that the move is now on hold and the state will stay in the current phase for another three weeks.

Nevada's mask order by Governor Steve Sisolak, also a Democrat, came two days after the state saw a single-day record for cases, most of them in Clark County, home to Las Vegas.

Caesars Entertainment Corp said earlier on Wednesday that masks would be required at all of its properties nationwide, while rival MGM Resorts International said in a statement that it will require masks for all guests and visitors inside public spaces at its US resorts starting on Friday.

Mayors from nearly a dozen cities in Miami-Dade County announced this week that masks will be mandatory in all public spaces, including outdoors when social distancing isn't possible. Some mask orders have been met with legal challenges.

Chen Yingqun contributed to this story.