Speaking launches tiny airborne droplets that can linger in the air for almost 15 minutes, new research has revealed.
Scientists found loud speech can produce thousands of oral fluid droplets per second which could be significant in the spread of Covid-19, Hull Live reports.
The research, led by the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania, could help explain how people with no symptoms are able to infect others in care homes, offices or cruise ships.
Experts found it took eight to 14 minutes for oral fluid droplets to disappear after measuring their size and spread with a laser in an unventilated environment.
The study did not involve coronavirus or any other virus, but looked at how people generate respiratory droplets when they speak.
Researchers wrote: “These observations confirm that there is a substantial probability that normal speaking causes airborne virus transmission in confined environments.”
According to the experts, these droplets still could potentially contain enough virus particles to represent an infectious dose.
The study considers frequent person-to-person transmission being reported in community and health care settings, and explains it is likely that it could be relevant for Covid-19.
The authors write: “Our laser light scattering method not only provides real-time visual evidence for speech droplet emission, but also assesses their airborne lifetime.
“This direct visualisation demonstrates how normal speech generates airborne droplets that can remain suspended for tens of minutes or longer and are eminently capable of transmitting disease in confined spaces.”
Lawrence Young, professor of molecular oncology at the University of Warwick, said: "The study convincingly shows that normal speech generates airborne droplets that can remain suspended in the air for tens of minutes or longer.
“This suggests that virus from an infected individual could be transmitted this way in confined spaces, however there is no direct analysis of the presence of viruses in the droplets or their ability to pass on infection.
“The work is a physical study using a laser scattering method. One of the main assumptions in this paper is that each virus particle in a droplet is equally capable of causing an infection.
“We don’t know that this is the case for Sars-CoV-2 (Covid-19 ).
“The study is novel and supports the view that respiratory and aerosol transmission are significant mechanisms of virus spread.
“It does not really change our understanding of how this virus is transmitted, just confirms and extends previous data.
“It adds weight to the need for social distancing and raises important issues about the potential for the virus to spread in confined spaces such as offices and factories.
“It also highlights the problem of virus transmission from infected individuals who do not have symptoms.”
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