As the United States reported yet another record-breaking number of new coronavirus cases on Thursday, public health officials warned that younger Americans now account for an ever-growing percentage of infections.

In Arizona, where drive-up testing sites were being overwhelmed, nearly half of all cases are being seen in those aged 20 to 44, The New York Times reported. In Florida, which has been routinely breaking records for new cases in the past week, the median age of residents testing positive for the virus has dropped to 35, down from 65 in March. In Texas, where cases are soaring and hospitals are nearing capacity, young people now make up the majority of new cases in several urban areas, the newspaper said.

“What is clear is that the proportion of people who are younger appears to have dramatically changed,” said Joseph McCormick, a professor of epidemiology at UTHealth School of Public Health in Brownsville, Texas, told the Times. “It’s really quite disturbing.”

The troubling news came as the United States recorded nearly 40,000 new coronavirus cases on Thursday, the Washington Post reported.

COVID-19 infections in the United States had been slowing since the prior record of 36,739 cases back on April 24, but case counts have roared back in recent weeks, the Times reported.

Coronavirus cases are surging the most in the South and West. On Thursday, Florida Gov. Ron DeSantis said that he will not move his state to the next phase of reopening, while Texas Gov. Greg Abbott paused his state’s reopening and moved to free up precious hospital space for coronavirus patients, the Times said.

But the actual number of coronavirus cases is probably much higher than recent totals suggest, Dr. Robert Redfield, director of the Centers for Disease Control and Prevention, said Thursday. He estimated that the number of Americans who have been infected with the virus is most likely about 10 times the 2.4 million cases that have been reported, the Times reported.

In a sign that the White House is eyeing the latest coronavirus infection numbers with alarm, officials there said Thursday that the coronavirus task force will hold its first briefing in nearly two months on Friday, the Post reported.

A handful of states have brought the virus under control after being slammed in the early stages of the pandemic. Determined to keep case counts low, New York, Connecticut and New Jersey said Wednesday they will now mandate quarantines for travelers coming from states that are experiencing large spikes in new cases, the Times said. As of Thursday, that included residents of Alabama, Arizona, Arkansas, Florida, North Carolina, South Carolina, Texas and Utah.

By Friday, the U.S. coronavirus case count passed 2.4 million as the death toll climbed past 124,000, according to a Times tally.

According to the same tally, the top five states in coronavirus cases as of Friday were: New York with over 395,000; California with over 201,000; New Jersey with more than 172,000; Illinois with nearly 141,000; and Texas with almost 137,000.

Millions infected unknowingly in March

Meanwhile, a new study suggests that as many as 8.7 million Americans came down with coronavirus in March, but more than 80% of them were never diagnosed, CNN reported.

A team of researchers looked at the number of people who went to doctors or clinics with influenza-like illnesses that were never diagnosed as coronavirus, flu or any of the other viruses that usually circulate in winter. There was a giant spike in these cases in March, according to the study published June 22 in the journal Science Translational Medicine.

Only 100,000 cases were officially reported during that time period, and the United States still reports only 2.4 million cases as of Friday. But there was a shortage of coronavirus testing kits at the time, CNN reported.

The team turned to CDC data collected from each state for influenza-like illness. The agency asks doctors to report all cases of people coming in for treatment for fever, cough and other symptoms caused by influenza.

“The findings support a scenario where more than 8.7 million new SARS-CoV-2 infections appeared in the U.S. during March and estimate that more than 80% of these cases remained unidentified as the outbreak rapidly spread,” said Justin Silverman, of Penn State University, and colleagues, CNN reported.

Masking, social distancing

Meanwhile, White House Trade Advisor Peter Navarro said that the federal government was working to replenish the national stockpile of medical equipment and supplies in preparation for another surge of the virus this fall.

“We are filling the stockpile in anticipation of a possible problem in the fall,” Navarro told CNN. “We’re doing everything we can.”

Reimposing prior precautions could turn some states’ rising numbers around, experts say.

“Uniform masking would go a long way,” Dr. Scott Gottlieb, former commissioner of the U.S. Food and Drug Administration, said during an appearance on “Morning Joe” last week.

Dr. Peter Hotez, of the Baylor College of Medicine in Houston, said, “I don’t see any option other than to start re-implementing significant levels of social distancing.”

Hotez told CNN, “Things opened up prematurely. We didn’t complete that social distancing period that we needed to do, and now we’re seeing this very sharp acceleration.”

An old drug brings new hope

There was some good news last week, however. Researchers at Oxford University in England announced that dexamethasone, a widely used, low-cost steroid, appears to cut the death rate for ventilated COVID-19 patients by one-third. It also lowered the death rate for patients who require oxygen (but are not yet on a ventilator) by one-fifth, the Times reported.

“Bottom line is, good news,” Fauci, who directs the U.S. National Institute of Allergy and Infectious Diseases, told the AP. “This is a significant improvement in the available therapeutic options that we have.”

But at least three manufacturers of the drug reported shortages on Wednesday, according to the American Society of Health-System Pharmacists, STAT News reported. Two of the manufacturers cited increased demand as a reason for their shortages.

Meanwhile, the search for an effective vaccine continues. The U.S. Department of Health and Human Services (HHS) has said that it would provide up to $1.2 billion to the drug company AstraZeneca to develop a potential coronavirus vaccine from Oxford University, in England.

The fourth, and largest, vaccine research agreement funds a clinical trial of the potential vaccine in the United States this summer with about 30,000 volunteers, the Times reported.

The goal? To make at least 300 million doses that could be available as early as October, the HHS said in a statement.

The United States has already agreed to provide up to $483 million to the biotech company Moderna and $500 million to Johnson & Johnson for their vaccine efforts. It is also providing $30 million to a virus vaccine effort led by the French company Sanofi, the Times reported. Moderna said a large clinical trial of its vaccine candidate could begin in July.

Nations grapple with pandemic

Elsewhere in the world, the situation remains challenging.

Even as the pandemic is easing in Europe and some parts of Asia, it is worsening in India. Officials in New Delhi said Thursday that they planned to test all of the city’s 29 million residents in the next 10 days, as the nation careened toward 500,000 coronavirus infections and pushed many hospitals to their breaking point, the Times reported.

Brazil has also become a hotspot in the coronavirus pandemic, with more than 1.2 million confirmed infections by Friday, according to the Hopkins tally. U.S. President Donald Trump has issued a ban on all foreign travelers from Brazil because of the burgeoning number of COVID-19 cases in that country, CNN reported.

Cases are also spiking wildly in Russia: As of Friday, that country reported the world’s third-highest number of COVID-19 cases, at nearly 620,000, the Hopkins tally showed.

Worldwide, the number of reported infections passed 9.6 million on Friday, with almost 490,000 deaths, according to the Hopkins tally.

More information

The U.S. Centers for Disease Control and Prevention has more on the new coronavirus.