How Speech Propels Pathogens

Physics
Health

Speech and singing spread saliva droplets, a phenomenon that has attracted much attention in the current context of the Covid-19 pandemic. Scientists from the CNRS, l’université de Montpellier, and Princeton University1 sought to shed light on what takes place during conversations. A first study published in PNAS revealed that the direction and distance of airflow generated when speaking depend on the sounds produced. For example, the accumulation of plosive consonants, such as the “P” in “PaPa,” produces a conical airflow that can travel up to 2 metres in 30 seconds. These results also emphasize that the time of exposure during a conversation influences the risk of contamination as much as distance does. A second study published on 2 October in the journal Physical Review Fluids describes the mechanism that produces microscopic droplets during speech: saliva filaments form on the lips for the consonants P and B, for example, and are then extended and fragmented in the form of droplets. This research is being continued with the Metropolitan Opera Orchestra (“MET Orchestra”) in New York, as part of a project to identify the safest conditions for continuing this prestigious orchestra’s activity.

Projection of CO2 emitted by a member of the MET Orchestra while singing, recorded using an infrared camera. © M. Abkarian, P. Bourrianne and H.A. Stone (with help from the FLIR company and E. Bowman)
Production of saliva filaments on the lips. © M. Abkarian and H.A. Stone

 

  • 1. The French scientists work at the Centre for Structural Biology (CNRS/Université de Montpellier/Inserm) and the Alexander Grothendieck Institute of Montpellier (CNRS/Université de Montpellier).
Bibliography

Speech can produce jet-like transport relevant to asymptomatic spreading of virus. M. Abkarian, S. Mendez, N. Xue, F. Yang, H. A. Stone, Proceedings of the National Academy of Sciences, 25 september 2020 DOI : 10.1073/pnas.2012156117

Stretching and break-up of saliva filaments during speech: a route for pathogen aerosolization and its potential mitigation. M. Abkarian, H. A. Stone, Physical Review Fluids, 2 october 2020

Contact

Manouk Abkarian
CNRS researcher
Simon Mendez
CNRS researcher
Howard A. Stone
Professor at Princeton University, USA
Clara Barrau
CNRS Press Officer