Adults Found More Infectious than Children with SARS-CoV-2

Canadian children positive for SARS-CoV-2 were found less likely to grow the coronavirus in culture and had higher cycle thresholds and lower viral concentrations
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Canada (Coronavirus Today)

According to research published by the Canadian Medical Association Journal, children may be less involved in spreading the SARS-CoV-2 coronavirus to others.

Fourteen researchers from multiple disciplines at Canadian institutions analyzed samples from children and adults in Manitoba infected with SARS-CoV-2 to see if there was a difference in infectiousness. 

Using cell cultures of nasopharyngeal swabs, they investigated viral loads in both groups to determine if children were more infectious.

This study published on April 9, 2021, concluded children were not as infectious as adults.

Among 305 samples positive for SARS-CoV-2 by RT-PCR, 97 samples were from children aged ten years or younger, 78 were from children aged 11–17 years, and 130 were from adults (≥ 18 yr). 

Viral growth in culture was present in 31% of samples, including 18 (19%) samples from children ten years or younger, 18 (23%) from children aged 11–17 years, and 57 (44%) from adults (children v. adults, odds ratio 0.45, 95% confidence interval [CI] 0.28–0.72). 

The cycle threshold was 25.1 (95% CI 17.7– 31.3) in children ten years or younger, 22.2 (95% CI 18.3–29.0) in children aged 11–17 years, and 18.7 (95% CI 17.9–30.4) in adults (p < 0.001). 

The median TCID50/mL was significantly lower in children aged 11–17 years (316, interquartile range [IQR] 178–2125) than adults (5620, IQR 1171 to 17 800, p < 0.001). 

Cycle threshold was an accurate predictor of posi-tive culture in both children and adults (area under the receiver-operator curve, 0.87, 95% CI 0.81–0.93 v. 0.89, 95% CI 0.83–0.96, p = 0.6).

"Our findings have important public health and clinical implications," wrote principal investigator Dr. Jared Bullard, associate professor, pediatrics/child health and medical microbiology/infectious diseases, Max Rady College of Medicine, University of Manitoba, and associate medical director, Cadham Provincial Laboratory in Winnipeg, Manitoba. 

"If younger children are less capable of transmitting infectious virus, daycare, in-person school and cautious extracurricular activities may be safe to continue, with appropriate precautions in place, and with lower risk to child care staff, educators and support staff than initially anticipated."

Compared with adults, the study authors wrote that children with nasopharyngeal swabs that tested positive for SARS-CoV-2 were less likely to grow the coronavirus in culture. They had higher cycle thresholds and lower viral concentrations suggesting that children are not the main drivers of SARS-CoV-2 transmission.

"This is particularly important given the increased likelihood of asymptomatic infection in this group."

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