Four patients with #COVID19 infections wearing surgical masks, cotton masks and no mask coughed onto a petri dish 20 cm from their mouth.
They did not test N95 masks.
tinyurl.com/uoh524c
"Neither surgical nor cotton masks effectively filtered SARS–CoV-2 during coughs by infected patients."
Important point:
This "does not reflect the actual transmission of infection from patients with COVID-19 wearing different types of masks. We do not know whether masks shorten the travel distance of droplets during coughing"