Child COVID-19 cases accounted for nearly 25 percent of new infections reported over one week in late April, according to a joint report from the American Academy of Pediatrics and the Children's Hospital Association.
The number of child COVID-19 cases per 100,000 children was highest in several states across the Midwest and the southern and eastern regions, according to the April 29 report.
Of the 319,601 new infections reported from April 22 to 29, children represented 22.4 percent (71,649 cases) of the total, according to the research, which is based on the "best publicly available data" on child cases at the state level.
The report said there was an overall rate of 5,026 child COVID-19 cases per 100,000 children in the population.
Children represented 13.8 percent (3,782,724 cases) of all infections (27,320,708) reported in the U.S. from the start of the pandemic to April 29, it added. The study was based on data from 49 states that provided age distributions of COVID cases, plus Puerto Rico, Guam and Washington, D.C.
For New York, only New York City reported the age distribution of cases. Massachusetts has only released this information for new infections in the two weeks leading up to April 29. Texas reported the age distribution for only 3 percent of cases.
See the full report for more information.
States with highest number of child cases per capita
The figures below indicate the number of child COVID-19 cases per 100,000 children in the population, according to the April 29 report.
North Dakota 9,416.4 cases per 100,000 children
Tennessee 8,817.2
South Carolina 8,200.2
South Dakota 8,179.4
Connecticut 8,113.9
Arizona 7,588.7
Delaware 7,545.7
Wisconsin 7,538.0
Rhode Island 7,389.2
Minnesota 7,130.5
Why are the numbers rising?
The rising proportion of child COVID-19 cases could be down to a combination of factors, including new variants and the vaccine rollout among adults, according to Dr. Sean O'Leary, vice chair of the American Academy of Pediatrics' committee on infectious diseases.
"I think there are several things going on. One, of course, are the new variants that are circulating. This B.1.1.7 variant that's really becoming dominant in a lot of the country is more transmissible," O'Leary told NPR on Sunday.
"The jury is still a bit out on if it's more severe. It's not clear if it's particularly more transmissible in kids. But at this point, it appears it's just more transmissible in everyone," he added.
"In many parts of the country, depending on how states track their date—60 and older, 65 and older, 70 and older—very high proportions of those populations in some places have been vaccinated.
"But that, just by simple math, is going to change the proportion of cases that are happening in the other demographics."
The reopening of schools in parts of the country may also be playing a role. "We are seeing more outbreaks than we had related to school and school activities. We've seen those all along, and we're seeing a little bit more of those now proportionately than we had," O'Leary said.
In a briefing update on March 19, the U.S. Centers for Disease Control and Prevention said: "Although national COVID-19 case incidence rates among children and adolescents have risen over time, this trend parallels trends observed among adults."
The CDC added: "Significant secondary transmission of SARS-CoV-2 infection can and does occur in school settings when prevention strategies are not implemented or are not followed."
The wider picture
Coronavirus has infected more than 154.4 million people since it was first reported in Wuhan, China, including over 32.5 million in the U.S. More than 3.2 million people have died worldwide and over 91 million have recovered as of Wednesday, according to Johns Hopkins University.
The graphic below, produced by Statista, shows the share of the population fully vaccinated against COVID-19 in different countries.
The graphic below, also produced by Statista, shows the number of COVID-19 vaccine doses administered per 100 people in various countries.
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