Transcript for Arizona sees staggering number of pediatric COVID-19 cases
Rachel, thank you. You heard Rachel mention the virus spreading among the troops. There's also growing concern about the toll on American children as well. Nearly 2.5,000,000 children now testing positive Arizona alone tonight, cases involving children now five times the number we were seeing just last fall. Here's Marcus Moore on that tonight. Reporter: Tonight, with Arizona hospitals still overwhelmed with covid patients, the state now seeing the virus in a staggering number of children and teens. We are now the leading state in the country for covid positivity in children. Reporter: Nearly 1 in 7 covid cases now under the age of 20. Arizona's largest hospital system reporting a dramatic spike in the number of children admitted. They need IV fluids. They need extra support with oxygen. And about a third, just as adults who are hospitalized with covid, they need icu care. Reporter: As of mid-january, nearly 2.5 million children in the us have tested positive for covid since the start of the pandemic. Last week alone, seeing the highest weekly increase in new cases. For 13-year-old Maggie Flannery, her covid symptoms got increasingly worse. For two months her mother says she could not get out of bed. I had a lot of, like, aching in my body. My chest felt very heavy, and I had trouble breathing. Reporter: The onetime ballerina in New York has had to drop extracurricular activities due to the virus' long-term effects. And while severe cases of covid remain uncommon among children, doctors say they are seeing more instances of the rare multisystem inflammatory syndrome in children linked to the virus. In Texas, 11-year-old Cason Abbott has a long road to recovery after battling that rare covid-linked syndrome. With mis-c it has really affected him in such a different way as far just zapping him of his energy level. Reporter: Tonight therere a a pair of clinical trials under way. Moderna's is looking at age groups 12 to 17. Those have already started. And tonight pfizer has announced that its vaccine trials for children 12 to 15 are fully enrolled. And David, tonight, they are under way.
This transcript has been automatically generated and may not be 100% accurate.