Dödligt virus från Kina orsakar panik (SARS-CoV-2, COVID-19)

In all modelling scenarios, routine facemask use by 50% 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. 100% 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 facemask 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).

The team investigated the varying effectiveness of facemasks. Previous research shows that even homemade masks made from cotton t-shirts or dishcloths can prove 90% effective at preventing transmission.

The study suggests that an entire population wearing masks of just 75% effectiveness can bring a very high 'R' number of 4.0—the UK was close to this before lockdown—all the way down to under 1.0, even without aid of lockdowns.

In fact, masks that only capture a mere 50% of exhaled droplets would still provide a "population-level benefit", even if they quadrupled the wearer's own contamination risk through frequent face touching and mask adjustment (a highly unlikely scenario).