Chatting spreads Covid-19 more than COUGHING: Half-a-minute talk without a face mask can pose greater risk of coronavirus infection than a brief cough, study finds
- Study found talking can pose a greater risk of Covid infection than coughing
- Speaking without a face mask for 30 seconds poses a greater risk of spread
- University of Cambridge and Imperial College scientists conducted the study
Talking for 30 seconds without a face mask in a poorly-ventilated room can pose a greater risk of Covid infection than coughing for half a second in front of someone, a study found.
While coughing quickly produces a larger number of big droplets, speech releases more small droplets which hang in the air for an hour, said scientists from the University of Cambridge and Imperial College London.
Lead author Dr Pedro de Oliveira told the journal Proceedings of the Royal Society A: ‘People are very aware of the risk of a cough, and used to protecting others by coughing into their arm or a tissue.
‘While we cannot really speak into our arms, we can reduce the risk of transmission by wearing a mask to protect both ourselves and others.’
Talking for 30 seconds without a face mask in a poorly-ventilated room can pose a greater risk of Covid infection than coughing for half a second in front of someone, a study by the University of Cambridge and Imperial College London found (stock photo)
The new research may surprise many in highlighting a greater risk from a chat than a cough.
The researchers estimate that a room full of students in a lecture hall, for example, could have up to a one in five chance of being infected by the lecturer speaking without proper ventilation.
The study confirms that in the first few seconds after it happens, a cough carries a greater risk than 30 seconds of speech.
Someone standing within two metres of a coughing person with Covid has up to a 50 per cent chance of being infected, thanks to the force of the cough and the large droplets released.
The risk of infection from someone with Covid speaking is, by comparison, 10 per cent within the first few seconds.
However, while half a minute of speech and a half-second cough produce roughly the same amount of exhaled liquid, the droplets from someone speaking tend to be smaller.
That means they are more likely to linger in the air, rather than heavily falling to the ground, based on the mathematical models.
The researchers used these models to calculate the amount of virus contained in droplets from people’s mouths and how they evaporate and settle, taking into account factors like air flow, drag and humidity.
The researchers estimate that a room full of students in a lecture hall, for example, could have up to a one in five chance of being infected by the lecturer speaking without proper ventilation (stock image)
They put the risk of someone being infected by an hour of talking, under specific conditions, in a poorly ventilated room, at up to 20 per cent.
But this falls to seven per cent at most if that room is very well ventilated, with air flow to remove the virus.
Even when someone is two metres away, the calculations suggest the virus in very small droplets from a cough can reach them within one to two seconds, while virus from speech takes five to 10 seconds.
The researchers have created a free online tool, called Airborne.cam, which helps to work out how ventilation and mask use can help to reduce the risk of indoor transmission, and how that risk changes over time.
Savvas Gkantonas, co-author of the study from the University of Cambridge, said: ‘The tool can help people use fluid mechanics to make better choices, and adapt their day-to-day activities and surroundings in order to suppress risk, both for themselves and for others.’
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