More than 70,000 new COVID-19 cases in children have been reported across the U.S. since early August, new data shows.

Child cases increased by 21% between August 6 and August 20, according to from the American Academy of Pediatrics and the Children's Hospital Association. More than 440,000 children have been infected in the U.S. since the start of the pandemic, the report said.

Despite the climbing numbers, severe illness in children from the virus is rare, the report said. But updated guidance from the U.S. Centers for Disease Control and Prevention report . Of those hospitalized with the virus, about one in three children is admitted to intensive care -- the same as adults.

The new data reflects what experts have highlighted: while the risk for COVID-19-related complications seems to be lower, there are still a lot of unknowns when it comes to children and the virus -- including how big their role is in transmitting it.

As several Georgia schools moved forward with reopening earlier this month, were asked to quarantine after districts reported COVID-19 cases among them.

In Florida, a legal battle may determine when students will make a physical return to class. The Florida Education Association, a teachers' union, sued after the state announced all schools would have to reopen this month. A judge blocked that requirement Monday with a temporary injunction and the state has since appealed.

In Mississippi, nearly 4,000 students and close to 600 teachers are quarantined due to COVID-19 exposure, officials said. During a news conference Tuesday, state health officer Dr. Thomas E. Dobbs III announced 144 new teacher cases and 292 student cases for last week.

"These numbers that we're seeing in our schools are not unexpected," Mississippi Gov. Tate Reeves said during the news conference. "I am pleased the number of isolations that we're seeing, the quarantines that we're seeing."

"And I'm pleased that there are a large number of Mississippi kids that are sitting in a classroom right now learning in a safe environment and so we got to continue to monitor it, we've got to continue to be careful," he added.

Officials recommend more aggressive measures in Georgia

While cases nationally have been on the decline and the experts still point to several areas of concern.

Those include the country's heartland, which CDC Director Dr. Robert Redfield said last week seemed "" as other parts of the country were jotting improvements in their COVID-19 trends. The key, Redfield said, is to stick with mitigation measures, which have helped drive cases of the virus down.

According to the White House Task Force for the virus, there are more points of concern.

The Atlanta Journal-Constitution and WABE first reported on the group's latest report which says Georgia's improvements remain fragile and the state could suffer more without further aggressive actions to control the spread of the virus, including a statewide mandate on masks and shutting down bars in areas with high transmission rates.

Georgia is among only a handful of states -- including Florida -- that hasn't implemented a statewide mask requirement. Masks, experts have said for months, are currently among the country's most powerful tools when it comes to curbing the spread of the virus. An influential COVID-19 model updated its to show about 70,000 lives could be saved across the country in the next months if more Americans wore masks.

CNN reached out to the White House and the Task Force for comment but in the past they have repeatedly declined to make these reports public.

Candice Broce, a spokeswoman for the governor, said in an email, "Since the last Coronavirus Task Force report was leaked to the AJC, our new cases per 100,000 people has dropped by 22.68%." The report was dated August 23.

In the last seven days, cases across Georgia have declined by 12%. Over the last two weeks, the state has seen a 26.26% decrease in cases, according to an analysis of data from Johns Hopkins University.

The governor has defended the state's COVID-19 strategies and Broce added the task force report, which CNN has not independently verified, shows "Georgia is making progress and has seen a decrease in new cases and a decrease in test positivity over the last week."

But for the second week in a row, Georgia is among the worst in the nation for new cases.

On Tuesday, the state's health department reported 2,236 new cases of the virus, bringing the state's total infections to more than 258,000. It is the state with the fifth highest number of infections in the U.S., according to Johns Hopkins.

Hopeful news in California

In California, which saw a rapid surge of cases over the summer, health officials are now saying the numbers seem to show a stabilization of transmission.

The state's positivity rate is down from two weeks ago, a month ago and two months ago, said State Health and Human Services Agency Secretary Dr. Mark Ghaly.

In Los Angeles, health officials reported less than 1,000 new cases on Tuesday for the first time since early June. In July, the daily number of new cases averaged at about 3,200 each day, a from the county health department said.

"Last week, we mentioned that we were showing progress on meeting the state's benchmarks for getting off the watch list, and we are grateful for everyone's sacrifices that have resulted in slowing the spread," Dr. Barbara Ferrer, the county's director of public health, said in a statement.

"Because of the lessons we learned from our explosion of cases in July, I need to ask that we continue to significantly modify our actions if we want to keep community transmission rates low."

California still leads the country with the highest amount of infections reported -- more than 680,000 cases since the start of the pandemic.