two schoolchildren wear masks and backpacks
(Kelly Sikkema /Unsplash)

University of Guelph researchers have revealed that more than one-third of total positive cases among children in Ontario are asymptomatic, emphasizing the need for targeting asymptomatic and mild infections in efforts to control the spread of COVID-19.

Led by Dr. Ed McBean, a team of researchers analyzed data from nearly 220,000 positive cases in Ontario over the last year.

“This is worrisome as undocumented COVID-19 cases in children could cause the rapid spread of silent COVID-19 transmission in communities,” said McBean, a professor in U of G’s School of Engineering who worked on the study with engineering PhD student Brett Snider and undergraduate engineering student Bhumi Patel.

The research team found that children under nine were most likely to be asymptomatic (35 per cent) or only have one symptom (31 per cent). A fever was the most common single symptom for children under nine at 30 per cent.

Overall cases were milder in children and very few showed signs of a cough – a frequent symptom in adults over the age of 40.

Dr. Ed McBean

“Our findings indicate that asymptomatic and pre-symptomatic cases are substantial in number,” said McBean. “This highlights the importance of targeting asymptomatic and mild infections in the continuing effort to control the spread of COVID-19.”

Published recently in Infectious Disease Reports, the study used data obtained from the Ontario Ministry of Health and consisted of 219,075 individual cases that tested positive from more than 8.4 million COVID-19 tests performed throughout Ontario between January 2020 and January 2021.

The positive tests were classified by symptoms including cough, fatigue, fever, headache, shortness of breath, sore throat and ‘no symptoms’. Other variables such as population demographics, co-morbidities and how the virus was acquired were also included.

“There is a broad range of severity of illnesses from COVID-19 making asymptomatic infections important to understand because the virus can still be transmitted causing critical illness in others,” said McBean.

Despite the province’s current stay-at-home order, McBean said, asymptomatic testing  is still useful.

“Given the fact that more than 30 per cent of children with the virus are asymptomatic, it would be effective to invest in testing to identify asymptomatic children in situations where children are not wearing masks, such as in daycares, and are in close proximity to other children or adults such as multi-generational homes and daycares.”


Dr. Ed McBean