April 23, 2020 / 4:00 PM / a month ago

Partly false claim: Wear a face mask; COVID-19 risk reduced by up to 98.5%

Illustrations widely shared on social media claim to show the percentage decreases in the risk of COVID-19 contagion when people wear face masks. ( here , here , here , here )

The illustration has also been shared in multiple languages including Catalan ( here ), French ( here ) Burmese( here ) and Spanish ( here ).

The diagram in the illustrations makes the following claims: There is a 70% contagion probability between a COVID-19 carrier not wearing a mask and a non-carrier wearing a mask; a 5% contagion probability between a COVID-19 carrier wearing a mask and a non-carrier not wearing a mask; and a 1.5% contagion probability between a COVID-19 carrier and a non-carrier both wearing masks.

This claim is not substantiated. Although some health authorities recommend the use of masks to help limit the spread of COVID-19, Reuters could not find any evidence to back up these percentages.

The U.S. Centers for Disease Control and Prevention (CDC) told Reuters via email that wearing masks is recommended as a way of strengthening social distancing, but they do not have data to measure how this affects the risk of transmission.

“CDC can’t confirm the accuracy of the numbers reflected in this image. Currently we are not finding any data that can quantify risk reduction from the use of masks”, a CDC spokesperson told Reuters.

The CDC has publicly said that cloth face coverings are “not intended to protect the wearer, but may prevent the spread of virus from the wearer to others” ( here ).

The CDC spokesperson said a cloth mask is a way to contain respiratory secretions right at the source. “The mask traps the droplets before they spread into the environment. Therefore, ‘my mask protects you, and your mask protects me!’ It’s a way of strengthening the social distancing that we are already doing”, she said.

The European Centre for Disease Prevention and Control states: “It is not known how much the use of masks in the community can contribute to a decrease in transmission in addition to the other countermeasures” and stresses the use of masks should only be considered as “complementary” and not as a replacement for other established preventive measures. ( here )

As of April 22, 2020 the World Health Organization (WHO) continues to advise that the use of face masks alone is “insufficient to provide an adequate level of protection”. On a recent update to its guidelines ( bit.ly/3aueKzh ), the WHO warned of potential risks for healthy people wearing masks in community settings, including “self-contamination by touching and reusing (a) contaminated mask” and “false sense of security, leading to potentially less adherence to other preventive measures such as physical distancing and hand hygiene”.

VERDICT

Partly false: There is no data available to quantify risk reduction from the use of masks but they are recommended by some authorities, including the CDC in the United States, as a supplementary measure to strengthen other preventive steps such as social distancing and frequent handwashing.

This article was produced by the Reuters Fact Check team. Read more about our fact checking work   here  .

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