London: Widespread use of face masks combined with physical distancing and some lockdown can lower Covid-19 transmission and may prevent a second wave of novel coronavirus infections, say researchers.
A study suggests that lockdowns alone will not stop the resurgence of SARS-CoV-2 and that even homemade masks with limited effectiveness can dramatically reduce transmission rates if worn by enough people, regardless of whether they show symptoms.
"Our analyses support the immediate and universal adoption of face masks by the public," said lead author Dr Richard Stutt from the University of Cambridge in the UK.
"If widespread 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," Stutt added.
For the study, published in the journal Proceedings of the Royal Society, the research team worked to link the dynamics of the spread between individuals with population-level models, to assess different scenarios of face mask adoption combined with periods of lockdown.
The modelling included stages of infection and transmission via surfaces as well as air.
Researchers also considered negative aspects of mask use, such as increased face touching.
The reproduction or 'R' number -- the number of people an infected individual passes the virus onto -- needs to stay below 1.0 for the pandemic to slow.
The study found that if people wear masks whenever they are in public it is twice as effective at reducing 'R' than if masks are only worn after symptoms appear.
In all modelling scenarios, routine mask use by 50 per cent or more of the population reduced Covid-19 spread to an R less than 1.0, flattening future disease waves and allowing less-stringent lockdowns.
Viral spread reduced further as more people adopted masks when in public.
The findings showed that 100 per cent mask adoption combined with on/off lockdowns prevented any further disease resurgence for the 18 months required for a possible vaccine.
The models suggest that - while the sooner the better - a policy of total face-mask adoption can still prevent a second wave even if it isn't instigated until 120 days after an epidemic begins (defined as the first 100 cases).
Previous research shows that even homemade masks made from cotton t-shirts or dishcloths can prove 90 per cent effective at preventing transmission.
The researchers point out that crude homemade masks primarily reduce disease spread by catching the wearer's own virus particles, breathed directly into fabric, whereas inhaled air is often sucked in around the exposed sides of the mask.