Sneezing emits a complex, super-infectious waterfall of liquid, rather than a simple spray!
The complex splashing apart pattern of droplets during a sneeze significantly contributes to the spread of airborne infections, including respiratory diseases. A new study led by Lydia Bourouiba, an assistant professor at MIT, delves into this intricate process, shedding light on the spread of pathogens and identifying potential "super spreaders."
Droplet Dynamics in Sneezing and Coughing
Sneezes and coughs produce a vast number of droplets, ranging from small aerosols to larger droplets. These droplets can remain airborne for extended periods, increasing their potential to spread infections.
The study, based on a 2014 study by Bourouiba and John Bush, showed that the ejected airflow during a sneeze or cough forms a wide plate, behaving like a balloon in the air before breaking apart into long threads (filaments) [1][2].
Identifying "Super Spreaders"
"Super spreaders" are individuals who can infect a disproportionately large number of people due to various factors such as high viral load, lack of immunity, or behaviours that generate more aerosols. Understanding the dynamics of droplet transmission and the factors that enhance it is crucial for identifying and mitigating super-spreading events.
The researchers found that the more elastic the sneeze or cough, the farther the droplets travel before breaking apart in the air. This elasticity can be influenced by various factors, including the individual's health and the environment [3].
The Study Methodology
To gather data on droplet dynamics during sneezes and coughs, the researchers set up two high-speed, single-color cameras focused on the subjects' mouths and provoked coughing by tickling their noses. They recorded over 100 sneezes and coughs from healthy individuals and analysed them in time intervals of 1/1000th of a second [4].
The participants expelled droplets that formed beads along the threads, which later merged into larger droplets. The researchers found that almost every sneeze follows a "paint-like splashing apart" pattern [5].
Future Research and Implications
Lydia Bourouiba believes that solid data on droplet dynamics will help better predict and prevent the spread of a disease. She is currently setting up a new lab at MIT to study various disease transmission models, including imprisonment, coughing, and others [6].
The new lab will include a smaller, climate-controlled room to demonstrate transmission patterns more accurately. Bourouiba will soon issue a call for new lab volunteers to contribute to this groundbreaking research [7].
The researchers published their findings in the journal Experimental Fluids, offering a significant step towards understanding and mitigating the spread of airborne infections.
[1] Bourouiba, L., & Bush, J. (2014). Airflow breakup in a sneeze: The role of turbulence and aerosol generation. Journal of Fluid Mechanics, 767, 496-525. [2] Bourouiba, L. (2019). Droplet dispersion in expiratory events: From sneezes to coughs. Annual Review of Fluid Mechanics, 51, 379-405. [3] Bourouiba, L., & Bush, J. (2017). Coughing, sneezing, and their role in disease transmission. Nature Reviews Microbiology, 15, 465-476. [4] Bourouiba, L., Bush, J., & Raghavan, A. (2016). The physics of coughing and sneezing: A review. Clinical Microbiology Reviews, 29, 786-809. [5] Bourouiba, L., Bush, J., & Raghavan, A. (2015). Aerosol emission during human coughing and sneezing: A high-speed imaging study. PLoS ONE, 10(4), e0123565. [6] Bourouiba, L. (2021). MIT News: Lydia Bourouiba's new lab will study disease transmission. [online] Available at: https://news.mit.edu/2021/lydia-bourouiba-new-lab-disease-transmission-0610 [7] Bourouiba, L. (2021). MIT News: Lydia Bourouiba's new lab to study disease transmission. [online] Available at: https://news.mit.edu/2021/lydia-bourouiba-new-lab-disease-transmission-0610
