Silent transmitters could be responsible for half of covid-19 cases, study finds

Can asymptomatic people transmit covid-19? 1:45

(CNN) - Silent transmission could be responsible for half of all coronavirus cases in the United States, according to a study published Monday in the Proceedings of the National Academy of Sciences.

The term "silent transmission" means that the virus is transmitted through asymptomatic or presymptomatic patients, who are more difficult to find and track.

How the study worked: The study, led by Alison Galvani of Yale University and her colleagues, used existing coronavirus transmission models and research, which already indicated that asymptomatic infections account for 17.9% to 30.8% of all infections.

Based on these existing figures, the team found that presymptomatic individuals would account for 47% to 48% of transmission, and asymptomatic individuals would account for 3.4% to 6.6% of transmission.

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What this means: The team found that even immediate isolation of all symptomatic cases would not be enough to control the spread. Authorities would have to identify and isolate more than a third of the silent transmitters, as well as all symptomatic cases, to prevent an outbreak.

The researchers emphasized the need for testing and contact tracing to safely lift the current social estrangement and restrictions of staying home.