• I was involved in this study with the School of Public Health, the University of Hong Kong between 2013 and 2016. Our wonderful lead author is Nancy Leung.

The Significance (Research Gap)

• We wanted to quantify the effects of surgical face masks in reducing viral load in patients infected with seasonal influenza viruses or common cold viruses.

What We Did

• Recruited patients who show symptoms of upper respiratory infections, such as fever, cough, runny nose and sneezing.
• Collected samples from these patients, including the air they breathe out.
• We had a machine that could collect these air samples. It could also seperate the air into droplets (>5 μm) and aerosols (≤5 μm).
• Participants either wore a surgical face mask or didn’t.
• We ran tests to determine the type and amount of virus present (viral load), and compared the viral load in different patient samples.

Our Conclusions

• Different repiratory viruses may have different modes of transmission. 
• How easily a virus can be transmitted to others differs in different individuals too.
• We had different findings for different viruses.
• Surgical face masks are effective in reducing the viral load of influenza viruses in droplets, and seasonal coronaviruses in both droplets and aerosols, but not with rhinoviruses.
• This has important implications for control of COVID-19, suggesting that surgical face masks could be used by ill people to reduce onward transmission.