Pediatric COVID-19 cases in Mississippi 10 times higher than previously thought: Study

The number of children and adolescents with COVID-19 in Mississippi may be more than 10 times the number of previously reported cases, according to a new study.

Pediatricians have previously suggested that because children are more likely to have COVID-19 without showing any symptoms, many infections in children are never diagnosed.

Looking back at residual blood samples from people younger than 18 collected from May to September 2020, researchers at the University of Mississippi Medical Center, in collaboration with the Mississippi State Department of Health and the Centers for Disease Control and Prevention, measured levels of antibodies against SARS-CoV-2 .

They found that the percentage of samples positive for antibodies increased from 2.5% in May to 16.3% in September. Overall, their results suggested that an estimated 113,842 Mississippi children and adolescents had been infected by September 2020.

In contrast, only 8,993 cases were reported to the Mississippi Health Department by that time -- a figure that could be as much as 10 times less that the real number of children and adolescents infected in the state.

Of note, the samples are from children who needed bloodwork for other reasons and may not represent the actual population. Nevertheless, the authors and some experts note that the results from case-based surveillance likely underestimate the rate of infections.

Many children continue to test positive for COVID-19 and, despite limited statistics, more are believed to be positive than show in case rates, according to Dr. John Brownstein, an epidemiologist with Boston Children's Hospital and an ABC News contributor.

"It helps push the concept that young people are still involved in transmission of this virus and need to be accounted for," he said of the Mississippi study.

While severe illnesses may be rare in children, infection and transmission to peers and adults remains possible.

This study was released as restrictions -- such as mask mandates and business closures -- have been relaxed in at least 11 states, and with many children returning to school.

The New York Times reported this week that based on its analysis of nationwide COVID-19 rates, only 4% of children live in counties where transmission is low enough for full-time, in-person learning without additional restrictions suggested by the CDC.

Tarun Jain, M.D., a combined internal medicine and pediatrics resident at McGovern Medical School at UTHealth in Houston, is a contributor the ABC News Medical Unit.