A report in Nature Magazine gives strong evidence that face masks are effective in reducing transmission of Coronavirus.
The scientists selected a sample of 246 volunteers, half of whom had coronavirus, influenza or rhinovirus. They split this group into two and gave one of the groups facemasks. Breath samples were then collected from each person.
The results clearly show the benefits of face masks:
We detected coronavirus in respiratory droplets and aerosols in 3 of 10 (30%) and 4 of 10 (40%) of the samples collected without face masks, respectively, but did not detect any virus in respiratory droplets or aerosols collected from participants wearing face masks