'No evidence' masks stop flu, WHO said in 2019

In 2019, the World Health Organization (WHO) reported that it had reviewed numerous studies which tested the efficacy of face coverings in stopping the transmission of the flu and found "no evidence that [wearing a mask] is effective in reducing transmission."

The review was part of a larger study examining "non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza."

Among the measures the study reviewed were hand-washing, quarantine protocols, school closures, "respiratory etiquette" and face masks.

On its website, currently, the WHO states that it "does not recommend [the] widespread use [of cloth face masks] among the public for control of COVID-19." Yet in the same paragraph it argues that governments should "encourage the general public to use non-medical fabric masks" in "areas of widespread transmission, with limited capacity for implementing control measures and especially in settings where physical distancing of at least 1 meter is not possible."

Scientists assert that coronavirus spreads primarily through respiratory droplets from infected individuals. Masks, including cloth face masks, are meant to stop those droplets from spreading to other individuals and to surfaces.