Coronavirus: Face masks are key to preventing second wave of Covid-19 - and we should all wear them, say University of Cambridge researchers
Face masks significantly reduce the transmission of the coronavirus - and we should all be encouraged to wear them, according to University of Cambridge researchers.
Their study shows even basic homemade masks could have a major impact if worn by enough people, regardless of whether they are displaying symptoms.
They say that lockdowns alone will not stop the resurgence of Covid-19, but further waves of the virus can be prevented if restrictions and physical distancing are also combined with population-wide use of face masks.
Critically, their modelling suggests that R or reproduction number - which measures the average number of people that a person with the virus infects - can be kept below the critical figure of 1.0, if enough people wear masks.
They called for governments to launch information campaigns that appeal to our altruistic side with messages like: “My face mask protects you, your face mask protects me.”
The study’s lead author, Dr Richard Stutt, is part of a team that usually models the spread of crop diseases at Cambridge’s Department of Plant Sciences.
He said:“Our analyses support the immediate and universal adoption of face masks by the public.
“If widespread face mask use by the public is combined with physical distancing and some lockdown, it may offer an acceptable way of managing the pandemic and reopening economic activity long before there is a working vaccine.”
Dr Renata Retkute, co-author and Cambridge team member, added: “The UK government can help by issuing clear instructions on how to make and safely use homemade masks.
“We have little to lose from the widespread adoption of facemasks, but the gains could be significant.”
Masks work by reducing the spread of airborne droplets.
The novel coronavirus is transmitted when infectious people exhale droplets loaded with the SARS-CoV-2 virus particles. This occurs particularly when people are talking, coughing or sneezing.
The Cambridge researchers linked the dynamics of spread between individuals with population-level models in order to assess different scenarios of face mask adoption, combined with periods of lockdown.
They modelled stages of infection and transmission via surfaces as well as air.
They took into account perceived negative aspects of mask use - such as the tendency of wearers to touch their face more, which can provide a route for the virus to enter the body.
Their study concluded that if people wear masks whenever they are in public it is twice as effective at reducing the ‘R’ number than if masks are only worn after symptoms appear.
And in the scenarios they modelled, routine face mask use by 50 per cent or more of the population reduced the spread of the virus and led to an R number less than 1.0.
This would flatten the curve in future waves of the disease and enable less-stringent lockdowns.
The more people adopt face masks when in public, the greater the reduction in viral spread.
If 100 per cent of the population wore face masks and lockdowns were switched on and off, a further resurgence of the virus could be prevented for the 18 months that may be needed to develop and deploy an effective vaccine, the researchers said.
The sooner the policy is adopted, the better, the modelling showed.
But total face mask adoption can still prevent a second wave even if it was not instigated until 120 days after the start of an epidemic, which is defined as the first 100 cases.
In the UK, this number was officially reached in early March, meaning the policy would need to be instigated within the next month.
In many countries around the world, where face masks are commonly worn due to air pollution, their adoption during the Covid-19 pandemic has been much more widespread than in the UK.
More than 50 countries - including France and Spain - have made them mandatory for those going out in public.
The UK government has come under criticism from some quarters for sending mixed messages on masks, initially suggesting that scientific advice on their benefits was limited, but subsequently advising everyone over the age of three to “wear a face covering in enclosed public spaces where social distancing isn’t possible and where you will come into contact with people you do not normally meet”, such as in crowded areas and shops.
From Monday (June 15), wearing a face covering is mandatory on public transport in the UK, and for any visitors to hospitals.
Anxious that hospitals and doctors do not run out of effective PPE (personal protective equipment), the government has stressed that surgical masks should be reserved for those working in healthcare or those exposed to dust hazards.
It also offers guidance on making masks at home, and said the key factor is that the nose and mouth is covered.
The government’s position has reflected guidance from the World Health Organization (WHO), which updated its guidance on June 5.
For months, WHO insisted there was not enough evidence to warrant making them mandatory, and warned that wearers may touch their face more or get a false sense of security and reduce their hand hygiene.
But amid emerging evidence that people with Covid-19 can be highly infectious before showing symptoms, it altered its guidance, telling governments to “encourage the general public to wear masks where there is widespread transmission and physical distancing is difficult, such as on public transport, in shops or in other confined or crowded environments”.
Earlier research has shown that homemade masks made from cotton T-shirts or dishcloths can be 90 per cent effective at preventing transmission of the virus.
And a review and meta-analysis of 172 studies from across 16 countries and six continents published in The Lancet concluded: “Face mask use could result in a large reduction in risk of infection.”
The Cambridge team’s new study explored the impact of masks of varying effectiveness.
They found that if the entire population wore masks of just 75 per cent effectiveness, it could bring down a very high R number of 4.0 - which the UK was close to before lockdown - to under 1.0, even without aid of lockdowns.
Even masks that only capture 50 per cent of exhaled droplets would still provide a 'population-level benefit', the study says, even in the highly unlikely scenario that they quadrupled the wearer’s own contamination risk, due to frequent face touching and mask adjustment.
Such crude homemade masks are primarily effective at reducing the spread of disease by catching the wearer’s own virus particles, which are breathed directly into fabric. Inhaled air is still sucked in around the exposed side of such masks.
Prod John Colvin, co-author from the University of Greenwich, said: “There is a common perception that wearing a face mask means you consider others a danger.
“In fact, by wearing a mask you are primarily protecting others from yourself.
“Cultural and even political issues may stop people wearing face masks, so the message needs to be clear: my mask protects you, your mask protects me.
“In the UK, the approach to face masks should go further than just public transport. The most effective way to restart daily life is to encourage everyone to wear some kind of mask whenever they are in public.”
The study, published in Proceedings of the Royal Society, could have profound implications beyond the UK.
Prof Chris Gilligan, co-author from Cambridge’s Epidemiology and Modelling Group in the Department of Plant Sciences, added: “These messages will be vital if the disease takes hold in the developing world, where large numbers of people are resource poor, but homemade masks are a cheap and effective technology.”
More by this authorPaul Brackley
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