COVID Spread More Indoors by Talking Than Coughing, Study Suggests

Talking may spread COVID more than coughing, according to scientists who have created an app to help calculate the risk of passing on the virus in different settings.

The team based in the U.K. also found social distancing at 2 meters (6.5 feet) in a poorly ventilated room was unlikely to protect others from the virus.

The study adds to existing research suggesting COVID can spread in big droplets that result from coughs, as well as in smaller aerosol particles emitted when we speak and breathe.

The authors of the paper published in the journal Proceedings of the Royal Society A created a computer model to predict how COVID spreads from an infected person. The model featured data on what happens when liquid droplets and aerosol particles of different sizes are released when we cough and speak, as well as how much virus these may carry.

The team also considered how long COVID stays viable outside the body, how much virus an infected person carries, and the dose of virus a person needs to get infected. The latter was based on data from another member of the coronavirus family of germs.

Based on this, the team created a website, Airborne.cam, enabling users to calculate how ventilation may affect the spread of COVID indoors.

The team found a short cough appeared to give off as much liquid as a person speaking continuously for 30 seconds. However, speaking seemed to carry more virus than coughing.

Their research also suggests it takes "only a few seconds" for virus particles at levels above the amount needed to infect a person to travel 2 meters (6.5ft). This implies that social distancing in poorly ventilated spaces will likely not protect people against the virus for long periods of time, the scientists wrote.

As such, the team concluded it is not safe for people not wearing personal protective equipment like masks to be within 2 metres of an infected individual who has coughed or spoken continuously in an indoor setting.

In addition, the study suggested that speaking for one hour in an unventilated room would raise the risk of infection by 10 to 20 percent for others. The risk was reduced by at least a factor of three if the air was changed 10 times per hour.

The authors from the University of Cambridge and Imperial College London wrote: "ventilation (in terms of both magnitude and direction) is of utmost importance in minimizing infection risk indoors."

Co-author Pedro Magalhães de Oliveira, research associate in experiments in spray combustion at the University of Cambridge, told The Guardian: "You need masks, you need distancing and you need good ventilation so these particles don't build up in an indoor space and they are safely removed."

Highlighting the limitations of the study, Catherine Noakes, professor of environmental engineering for buildings at the University of Leeds, who did not work on the paper, said the findings were based on assumptions. She said the amount of virus a person carries and the stage of their illness can affect their viral load.

She said: "It is likely that the results represent realistic worst-case scenarios as the model uses quite a high viral load as one of the assumptions, and this has a significant influence on the risk that is predicted."

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A stock image shows two women speaking. Scientists believe speaking may spread more COVID than a cough. Getty