Coronavirus: Symptomatic children carry more virus than those without symptoms, study suggests

  • Data from US and Canadian hospitals suggest that asymptomatic children carry lower coronavirus viral loads than those with symptoms.
  • The study included over 800 paediatric patients who tested positive for SARS-CoV-2.
  • Questions still remain, but the researchers are stressing the importance of hand hygiene and face masks. 

Children who test positive for the new coronavirus, but are asymptomatic (don't display symptoms) have significantly lower levels of the virus compared to those who experience symptoms.

This was according to a new study based on an analysis of 817 children from nine hospitals in the US and Canada who tested positive for SARS-CoV-2.

The findings were published in the Journal of Clinical Microbiology.

Although the study was the first large and comprehensive analysis of SARS-CoV-2 viral loads in asymptomatic children, the authors cautioned that the reason behind their finding was still unclear and required further research.

"While these findings provide some reassurance about the safety of asymptomatically infected children attending school, these unanswered questions suggest that risk mitigation measures in daycares, schools and the community remain critical to reduce the spread of Covid-19," said lead author and epidemiologist, Larry Kociolek of the Northwestern University in Illinois.

'Children must continue to wear masks'

The study included 339 asymptomatic and 478 symptomatic children (ages 0–17 years). All children in the study tested positive for the virus through polymerase chain reaction (PCR) tests.

Asymptomatic children who had either diabetes or recently had contact with a known Covid-19 case were more likely to have high viral loads.

"Children must continue to wear masks, maintain physical distance and wash their hands frequently," said Kociolek, adding that at this stage, the researchers could not predict which children were likely to carry more or less virus, as every age group they tested showed asymptomatic children with a higher viral load.

However, the team also found that, even in this group of asymptomatic cases with the highest viral loads, mean levels were still significantly lower than in the equivalent symptomatic group of patients.

Questions that still remain

"We now need to know what the peak viral loads are in asymptomatic kids with Covid-19," said study co-author and pathologist, Nira Pollock of the Boston Children's Hospital and the Harvard Medical School.

"Did the timing of testing just miss the peak in many of the asymptomatic kids in this study, or do asymptomatic kids actually have lower peak viral loads than symptomatic kids?'

Pollock also commented on the importance of recognising that rapid antigen tests had a limited detection capability, and that many of the asymptomatic children in their study likely would have tested negative using the rapid tests.

According to the Centers for Disease Control and Prevention (CDC), antigen tests were relatively inexpensive and can deliver results in approximately 15 minutes. Antigen tests for SARS-CoV-2, the health institute noted, were generally less sensitive than viral tests that detected nucleic acid using reverse transcription PCR (RT-PCR).

"Many of the asymptomatic kids in our study likely would have tested negative using the rapid tests based on our understanding of the limits of detection of those tests.

"Our findings should raise caution about using low sensitivity tests for asymptomatic screening programmes in paediatric populations," she said.

Based on the questions that remain at the forefront, the researchers encouraged further studies to better understand viral loads in asymptomatic children, especially peak viral loads during the early stages of infection.

READ | Children can carry Covid-19 virus in their respiratory tracts for weeks, study finds

READ | Coronavirus: ‘Silent spreaders’ may be carrying the same amount of virus as those with symptoms

READ | SA scientists to explore asymptomatic spread of the Covid-19 virus in the country

Image: Getty/Peter Dazeley

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