People With No Symptoms Spread Nearly 60% of COVID Cases, CDC Study Finds

The study indicates that many people won't know they're contagious based on their symptoms

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People without symptoms of COVID-19 are spreading the virus at a high rate and unknowingly becoming a source of many outbreaks, according to a new study.

A new model from U.S. Centers for Disease Control and Prevention researchers shows that nearly 60% of coronavirus transmission is coming from asymptomatic people, and experts believe this is adding to the uptick in cases being seen around the country.

The model, published Thursday in JAMA Network Open, assessed the spread of the virus by pre-symptomatic, asymptomatic and symptomatic individuals. It broke down that 59% of transmission by asymptomatic people further: 35% of all new cases came from people who infect others before they show symptoms and 24% from people who never developed symptoms at all.

The study indicates that many people won't know they're contagious based on their symptoms, which may be encouraging them to go about their daily lives with a false sense of safety. And it suggests people are most likely to catch the virus from someone who appears otherwise healthy.

Gov. Charlie Baker said Thursday the number of new COVID-19 cases has put a strain on the state's hospitals, causing him to extend the statewide coronavirus restrictions that are in place for another two weeks.

We need to remain vigilant, NBC News senior medical correspondent Dr. John Torres said.​

“These findings suggest that just identifying and isolating people who have symptoms isn't enough to control the ongoing spread of the coronavirus. It doesn't catch all the cases,” he said.

Some experts argue the model did not take into account the environment in which the spread occurs, or data on how the vaccine impacts asymptomatic infection.

Still, experts say it’s crucial to continue wearing a mask, keep social distance and take proper health and safety precautions.

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