More than 40% of people with COVID-19 never show symptoms, study finds

Health officials have long wondered how many people who get COVID-19 show no symptoms. Because those who don't feel sick rarely get tested, experts have only been able to estimate the number of such asymptomatic cases.

But new research now shows more than 40% of those who tested positive for COVID-19 were asymptomatic, according to the study published Tuesday in JAMA Network Open.

Researchers looked at 95 studies from January 2020 to February 2021 consisting of nearly 30 million people in Asia, Europe, North America, South America and Africa.

More than 60% of confirmed COVID-19 cases among people under 20 were asymptomatic; nearly 50% in people 20 to 39; about 32% in people 40 to 59, and about 33% in those over 60.

“Across the board, it showed that among the elderly, two-thirds had symptoms, and among the 20- to 30-year-olds, about two-thirds didn’t have symptoms,” said Dr. Alan Wells, medical director of UPMC Clinical Laboratories and professor of pathology at the University of Pittsburgh School of Medicine, who is not affiliated with the study. “That’s what we see in a lot of respiratory viruses.” ...