Aug. 25 (UPI) -- The percentage of asymptomatic children with COVID-19 is about the same as the rate of new cases in the surrounding community's population, according to a study published Tuesday.
This means that if 1.1% of the population in a region has COVID-19, with or without obvious symptoms, the same percentage of children might be infected with the virus despite not having a cough, fever or other signs, researchers at the University of California-San Francisco said.
In a city like San Francisco, where the standard class size for kindergarten through third grade is 22 students, a roughly 22% chance would exist that at least one child in each classroom has the disease, the researchers said.
The researchers' findings were published Tuesday by JAMA Pediatrics.
"Now, any group -- schools, hospitals, childcare facilities -- that wishes to estimate the prevalence of [COVID-19] infection in their community can do so with some confidence, based on the publicly available data," co-author Dr. Dylan Chan told UPI.
Chan, an associate professor of otolaryngology at the university, said that -- even with screening for symptoms -- the first step in evaluating any of these groups of children is to estimate the chance that one is infected but asymptomatic.
Determining the number of children with COVID-19 in a given population, even when they don't have symptoms, is "critical" information for communities as they begin to reopen schools and daycare facilities after months of lockdowns, Chan and his colleagues said.
To date, estimates of asymptomatic children have been based on a series of small studies, with patients who were screened for the virus when they visited hospitals or clinics for other healthcare services, the researchers said.
For the analysis, the team calculated the prevalence of positive COVID-19 test results -- 2.2% -- in just over 33,000 children without symptoms at 28 children's hospitals across the United States between May 1 and 29.
They then compared these figures to numbers of new cases in the communities surrounding these hospitals, based on data from the Johns Hopkins COVID-19 tracker, and found the "strong association" between the prevalence of the virus in children who are asymptomatic and current weekly incidence in the general population.
"Even in regions that had quite low case counts, cases of asymptomatic children with [COVID-19] infection were detected, so ... it will be virtually impossible to eliminate risk in a large school without aggressive [prevention] measures," Chan said.