Do a small number of patients carry high loads of the coronavirus even if they don’t show any symptoms?

Multiple studies have found that people showing no COVID-19 symptoms can carry as much of a transmissible load of the coronavirus as evidently ill patients. Since the load, or amount of virus present in an infected person’s body, is the biggest factor in transmitting the disease, this adds to the challenge of trying to track and manage the spread of COVID-19.

Studies published in leading medical journals in the U.S. and the U.K. have found viral presence to be similar whether infected people are symptomatic or asymptomatic. A third study found that “viral loads of asymptomatic patients were…significantly higher.”

A 2021 study noted that high viral loads are concentrated among a very small number of infected people, both symptomatic and asymptomatic, for reasons not yet understood. “Just 2% of infected individuals carry 90% of the virions circulating within communities,” it found.