Only about 20% of infected people remain symptom-free while they carry the new coronavirus, according to a review of 79 COVID-19 studies. These studies involved just over 6,600 people, of whom 1,287 remained asymptomatic. … The new figure of around 20% is at the low end of previous estimates of asymptomatic COVID-19 cases, said Dr. Susan Kline, a professor of infectious diseases with the University of Minnesota in Minneapolis.