Dr. Ashish Jha, dean of the Brown University School of Public Health, said he agrees with the CDC's ruling to shorten isolation time from 10 days to five days for asymptomatic people with COVID-19. That must be followed by five days of mask wearing around others.

Jha told "Good Morning America" on Tuesday that five days is enough to stop the spread for asymptomatic people because most people are contagious in the couple days before they have symptoms and in the two to three days symptoms begin.

But Jha said he think it would "make a big difference" if the CDC required COVID-19 patients to get a negative test before leaving isolation.

"I don’t know why the CDC did not put that in -- I suspect it might be because tests are still hard to come by," he said.

Rep. Bobby Rush, D.-Ill., said he tested positive for COVID-19 on Monday.

"Today, after being notified of a recent exposure, I tested positive with a breakthrough case of COVID-19," Rush said in a statement. "Fortunately, I am fully vaccinated and recently received my booster shot. I am feeling fine and currently have no symptoms."

Rush said he would begin quarantining. He encouraged everyone to get vaccinations and booster shots.

Amidst the nation's latest COVID-19 surge, nearly 200,000 more children tested positive for COVID-19, last week, up by about 50% since the beginning of December, according to a new report from the American Academy of Pediatrics (AAP) and the Children’s Hospital Association (CHA), released on Monday.

This week marks the twentieth consecutive week that pediatric COVID-19 case total has been above 100,000.

COVID-19 cases among children are "extremely high," and increasing, the organizations wrote.

Children accounted for about 20% of reported weekly COVID-19 cases, last week. For context, children, under age 18, make up 22.2% of the U.S. population.

COVID-19 related hospitalizations among children are also on the rise. On average, about 260 children in the U.S. are being admitted to the hospital with COVID-19 each day, according to federal data, and nearly 2,000 children are currently hospitalized with the virus.

To date, 22.4 million children ages 5 to 17 years-old -- about 42% of that population -- have received at least one dose of a COVID-19 vaccine.

-ABC News’ Arielle Mitropoulos

Delta Airlines announced it is working fast to implement the U.S. Centers for Disease Control and Prevention's latest guidance to reduce the isolation period for some infected patients.

Delta was one of many airlines to call on the federal government to reduce the isolation period from 10 days to five, citing staffing shortages that led to flight cancelations.

"The updated guidance allows more flexibility for Delta to schedule crews and employees to support a busy holiday travel season and a sustained return to travel by customers," the airline said in a statement.

Delta did not give more details as to when their new policy will take effect.

-ABC News' Mina Kaji

More free COVID-19 testing sites opened in New York City subway stations as several train lines were suspended due to understaffing.

The testing program, which was launched on Monday, originally only included the Grand Central Terminal station and the Times Square-42nd Street subway station -- two of the busiest stations in the city.

However, five more opened Thursday including two in Queens, one in the Bronx, one in Brooklyn and one in Manhattan.

It comes as the Metropolitan Transit Authority announced it is suspending three subway lines due to staffing shortages linked to COVID-19.

"Like everyone in New York, we've been affected by the COVID surge. We're running as much train service as we can with the operators we have available," the MTA said in a statement.

The B and Z subway lines are suspended all day Thursday along with the W line, which was also suspended on Wednesday.