In most cases, the illness was mild and short. Children were sick for six days, on average, and experienced an average of three symptoms. The most common symptoms were headache and fatigue.
But a small subset of children experienced lingering symptoms, including fatigue, headache and a loss of smell. Children between 12 and 17 were sicker for longer than younger children and more likely to experience symptoms that lasted at least four weeks.
“We hope our results will be useful and timely for doctors, parents and schools caring for these children — and of course the affected children themselves,” Dr. Duncan said.
The researchers also compared children who tested positive for the coronavirus with those who reported symptoms in the app but tested negative for the virus. Children who tested negative — and may have had other illnesses, such as colds or the flu — recovered more quickly and were less likely to have lingering symptoms than those with Covid. They were ill for three days, on average, and just 0.9 percent of children had symptoms that lasted at least four weeks.