The number and rate of coronavirus cases in children in the U.S. have been "steadily increasing" between March and July, according to new guidance released Friday by the CDC. The surge in cases comes as schools across the country struggle with returning to in-person learning. While children make up about 22% of the nation's population, they only account for about 7.3% of all COVID-19 cases, as of August 3. The CDC said that tracking coronavirus cases in children has been difficult due to a lack of widespread testing and the prioritization of testing for adults. The CDC said that transmission of the virus among kids may have been lower in the spring and summer due to strict stay-at-home orders, warning that trends are likely to change after the return to in-person learning and other activities.