Health experts say children make up more than 7% of all coronavirus cases in the U.S. -- while comprising about 22% of the country's population -- and the number and rate of child cases have been "steadily increasing" from March to July.

The data was posted alongside updated guidance from the U.S. Centers for Disease Control and Prevention for pediatricians that also includes what is known about the virus in children.

"Recent evidence suggests that children likely have the same or higher viral loads in their nasopharynx compared with adults and that children can spread the virus effectively in households and camp settings," the guidance states.

Transmission of the virus to and among children may have been reduced in spring and early summer due to mitigation measures like stay-at-home orders and school closures, the CDC says.

But now, schools and universities across the country are reopening and in some cases have had to readjust their approach following positive tests among students and staff. How to safely welcome students back has been an ongoing debate between local and state leaders as some push for a return to normalcy and others fear returning to class could prove deadly for some. In some cases, teachers have opted to resign rather than risk contracting the virus.

"So if I'm put into a classroom of 30 or more kids, it's a small room, there's one exit, the ventilation isn't all that great for schools," Arizona teacher Matt Chicci, who quit his job, told CNN. "It's not a good situation."

In Georgia, where several districts reopened in recent weeks, more than 1,000 students and staff were asked to quarantine following cases of coronavirus or exposures to someone infected.

North Paulding High School, which came under scrutiny when a student shared a photo of a crowded hallway days after school reopened, reported 12 cases in school and 21 total cases during the week of August 8 to 14.

The Paulding County School District (PCSD) says, "Cases in School is the number of confirmed cases of COVID-19 who spent at least some time on a school campus during the week reported."

The phrase "total cases" refers to the "Cases in school" and also "Students/staff who may have been out of school for any reason and tested positive; Students/staff who were identified as close contacts in another case and then tested positive while in quarantine; Virtual students who are enrolled at the school where they are listed but learn remotely online," the district says.

In Illinois, health officials are looking for people who attended an unofficial "mini-prom." At least five cases were linked to the event and 40 close contacts were identified.

While some U.S. officials -- including the President -- have downplayed the risk coronavirus positions on children, the new CDC guidance notes children can develop severe illness and complications, even if that risk is lower compared to adults. The rate of hospitalizations among children is increasing, the guidance says, and among those hospitalized, one in three children is admitted to intensive care -- the same as adults.

In the U.S., more than 5.3 million people have been infected with the virus and at least 168,446 have died, according to Johns Hopkins University.

Black and Latino populations hit hard in hotspots

Research published Friday from the CDC also showed that in hotspot counties across the US, Black and Latino people were hit hard by the virus, with a majority of the counties reporting disparities on coronavirus cases in one or more racial or ethnic groups.

"These findings illustrate the disproportionate incidence of COVID-19 among communities of color, as has been shown by other studies, and suggest that a high percentage of cases in hotspot counties are among person of color," said the authors.

In Milwaukee, Wisconsin, health officials say collecting coronavirus impact data by race helped them better strategize a response to the pandemic.

"[It] helped us alter our strategy so we could increase our outreach, add additional testing sites, just really help our communities of color prevent their exposure to COVID-19," said Jeanette Kowalik, commissioner of health at the Milwaukee Health Department.

Kowalik said the data drove conversations that wouldn't have taken place if officials weren't aware more people of color were impacted by the virus.

Doctors warn of lasting heart complications

With new evidence and data on the virus emerging almost weekly, health officials now have another warning: the risk of death from coronavirus-related heart damage seems to be far greater than previously thought, the American Heart Association said.

Inflammation of the vascular system and injury to the heart occur in 20% to 30% of hospitalized coronavirus patients and contribute to 40% of deaths, the association said Friday.

Dr. Mitchell Elkind, the association's president, said that the cardiac complications of COVID-19 could be "devastating" and linger after recovery.

The AHA said research indicates coronavirus could lead to heart attacks, acute coronary syndromes, stroke, blood pressure abnormalities, clotting issues, heart muscle inflammation and fatal heartbeat irregularities.

It's a statement that's long been hinted by coronavirus patients across the country, whose bodies were attacked in different ways by the coronavirus.

In Florida, a 21-year-old suffered heart failure while in the hospital and weeks since his recovery, his heart rate is still monitored and he's on medication for his blood pressure -- medications his doctors have said could continue for at least another year.

There is a critical need for more research, Elkind said.

"We simply don't have enough information to provide the definitive answers people want and need."