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Coughing may degrade a mask’s ability to prevent the coronavirus from being passed on, research suggests.
People in England must wear face coverings on public transport. More comfortable than masks, they are intended to act as a barrier against infectious droplets.
Hospital staff, however, are required to wear a medical-grade mask. This extra protection is also recommended for the elderly, people with pre-existing health conditions, and coronavirus patients and their carers.
Despite these guidelines, scientists from the University of Nicosia in Cyprus felt there was little evidence proving masks’ effectiveness.
After running a series of computer models, they found coughing breaks down the filter that “contains” the coronavirus.
A cough is one of the tell-tale symptoms of the infection, along with fever and a loss of taste or smell.
‘A mask will not provide complete protection’
The advice on masks amid the coronavirus outbreak has been somewhat muddled.
The World Health Organization (WHO) initially said there was no evidence a mask or similar fabric barrier wards off a viral respiratory infection, like the coronavirus.
It added, however, people carrying an airway virus who wear a mask are less likely to pass it on.
According to the WHO, new information suggests coverings may provide “a barrier for potentially infectious droplets”.
The Nicosia scientists previously found saliva droplets can travel up to 5.4 metres (18ft) in five seconds when an unmasked person coughs.
To better understand the effects of a mask, the team used computer models to map out the expected flow of small droplets.
Wind speed, air temperature, atmospheric pressure and humidity were all taken into account.
The temperature of the cougher’s mouth and surrounding skin were also adjusted for, with these influencing the projection of droplets.
Results, published in the journal Physics of Fluids, reveal masks can reduce airborne droplet transmission.
The filtering efficiency is affected, however, by repeated coughing.
The video was created with the droplets scaled up hundreds of times to visualise the effect.
Coughs and sneezes are the main way the coronavirus spreads.
The results suggest that even when a mask is worn, some droplets can travel up to one metre (3ft) if a patient coughs just mildly.
Without a mask, these droplets travel twice as far.
A mask may reduce the number of droplets that “leak” out the side of the fabric, but does not eliminate the risk entirely.
“The use of a mask will not provide complete protection,” said study author Professor Dimitris Drikakis.
“Therefore, social distancing remains essential.”
Hospital staff and care workers are unable to keep back from the coronavirus patients they treat.
They therefore require more extensive personal protective equipment, including disposable gloves, face shields and gowns.
Masks are also known to become less effective when wet, with everyone having moisture in their breath.
What is the coronavirus?
The coronavirus is one of seven strains of a virus class that are known to infect humans.
Others cause everything from the common cold to severe acute respiratory syndrome (Sars), which killed 774 people during its 2002/3 outbreak.
Since the coronavirus outbreak was identified at the end of 2019, more than 8 million cases have been confirmed worldwide, according to Johns Hopkins University.
Of these cases, over 3 million are known to have recovered.
Globally, the death toll has exceeded 437,000.
The infection has no “set” treatment, with most patients naturally fighting it off.
Those requiring hospitalisation are given “supportive care”, like ventilation, while their immune system gets to work.
Officials urge people ward off infection by washing their hands regularly and maintaining social distancing.
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