Masks for influenza patients: measurement of airflow from the mouth.

In case of a new influenza pandemic, provision of masks to coughing patients could be used to slow expansion of the epidemic. To quantitatively assess the efficacy of different masks, we used an ultrasonic anemometer to measure the velocity of airflow from the mouth in coughing. We found that even the cheapest paper masks reduced the air speed to less than 1/10, implicating their effectiveness in decreasing viral spread. We therefore propose that governments provide free masks to coughing patients in the general population upon the emergence of a new human influenza virus.