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PHILADELPHIA: Speech-generated droplets can remain airborne in a confined space for more than 10 minutes, a study published Wednesday (Thursday in Manila) showed, underscoring their likely role in the spread of the coronavirus.
Researchers from the National Institute of Diabetes and Digestive and Kidney Diseases asked a person to repeat aloud the phrase “Stay healthy” for 25 seconds in a closed box. A laser projected onto the box illuminated the drops, allowing them to be seen and counted.
They stayed in the air for an average of 12 minutes, the study published in the journal Proceedings of the National Academy of Sciences in the United States of America showed.
Taking into account the known concentration of coronavirus in saliva, the scientists estimated that each minute of speaking aloud can generate more than 1,000 drops containing viruses capable of remaining in the air for eight minutes or more in an enclosed space.
“This direct visualization demonstrates how normal speech generates droplets in the air that can remain suspended for tens of minutes or more and are capable of transmitting disease in confined spaces,” the researchers concluded.
The same team had observed that speaking less loudly generates fewer drops, in a paper published in the New England Journal of Medicine in April.
If the level of infectivity of the coronavirus can be confirmed through speech, it could give scientific impetus to recommendations in many countries to wear a face mask and help explain the rapid spread of the virus.
