The report in JAMA Pediatrics reveals that children younger than 5 years with mild-to moderate COVID-19 have much higher levels of genetic material for the virus in the nose compared to older children and adults.
Researchers from the Ann & Robert H. Lurie Children’s Hospital of Chicago suggest the ability of younger children to spread COVID-19 might have gone unrecognized because schools and daycare were rapidly closed when the pandemic began and generally have stayed that way.
“We found that children under 5 with COVID-19 have a higher viral load than older children and adults, which may suggest greater transmission, as we see with respiratory syncytial virus, also known as RSV,” explained lead author Taylor Heald-Sargent, MD, PhD, pediatric infectious diseases specialist at Lurie Children’s and Assistant Professor of Pediatrics at Northwestern University Feinberg School of Medicine. “This has important public health implications, especially during discussions on the safety of reopening schools and daycare.”
The study notes that children are susceptible to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) but generally present with mild symptoms compared with adults.
It further points out that, in many cases, children drive spread of respiratory and gastrointestinal illnesses in the population, but that data on children as sources of SARS-CoV-2 spread have remained limited.
“Early reports did not find strong evidence of children as major contributors to SARS-CoV-2 spread, but school closures early in pandemic responses thwarted larger-scale investigations of schools as a source of community transmission,” the authors write. “As public health systems look to reopen schools and day cares, understanding transmission potential in children will be important to guide public health measures.”
That led to the finding that replication of SARS-CoV-2 in older children leads to similar levels of viral nucleic acid as adults, but significantly greater amounts of viral nucleic acid are detected in children younger than age 5 years.
To reach that conclusion, researchers performed SARS-CoV-2 reverse transcriptase–polymerase chain reaction (PCR) on nasopharyngeal swabs collected at various inpatient, outpatient, emergency department, and drive-through testing sites at a pediatric tertiary medical center in Chicago between March 23 and April 27, 2020.
This cohort included all individuals aged younger than 1 month to 65 years who tested positive for SARS-CoV-2; patients with symptoms suggestive of a COVID-19–compatible illness and/or high-risk exposures were tested. The final cohort included 145 patients with mild-to-moderate illness within 1 week of symptom onset.
The study team compared three groups:
• 46 were children younger than age 5 years;
• 51 were children aged 5 to 17 years
• 48 were adults aged 18 to 65 years.
Results indicate similar median (interquartile range) PCR amplification cycle threshold CT values for older children (11.1 [6.3-15.7]) and adults (11.0 [6.9-17.5]).
“However, young children had significantly lower median (interquartile range) CT values (6.5 [4.8-12.0]), indicating that young children have equivalent or more viral nucleic acid in their upper respiratory tract compared with older children and adults,” according to the authors. “The observed differences in median CT values between young children and adults approximate a 10-fold to 100-fold greater amount of SARS-CoV-2 in the upper respiratory tract of young children.”
Researchers performed a sensitivity analysis and observed a similar statistical difference between groups when including those with unknown symptom duration. They also identified only a very weak correlation between symptom duration and CT in the overall cohort (Spearman P = .22) and in each subgroup (young children, Spearman P = .20; older children, Spearman P = .19; and adults, Spearman P = .10).
“Our study was not designed to prove that younger children spread COVID-19 as much as adults, but it is a possibility,” Dr. Heald-Sargent advised. “We need to take that into account in efforts to reduce transmission as we continue to learn more about this virus.”
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