Airborne spread of coronavirus ---------------------------------- The World Health Organisation is reviewing evidence from more than 200 scientists who warn that microscopic particles of coronavirus can linger in the air for long periods, infecting people who breathe them in ---------------------------------- Image of sneeze in progress captures cone-shaped plume of saliva droplets expelled from mouth ---------------------------------- MAIN MODES OF COVID-19 TRANSMISSION ---------------------------------- Infected person emits virus-filled particles when they breathe, speak, cough or sneeze ---------------------------------- 1 Droplets: Around 5-10 microns* in size. Generally fall to ground or onto surfaces within 1-2 metres of infected person. Most frequent mode of transmission, according to WHO ---------------------------------- 2 Aerosols: Smaller than 5 microns. May hang in air and follow air currents, travelling tens of metres – much greater than scale of typical room – before falling to ground ---------------------------------- *1 micron equal to one millionth of a metre ---------------------------------- RECOMMENDATIONS Ventilation systems should supply clean outdoor air and minimise recirculating air, particularly in public buildings, businesses, schools, hospitals and care homes General ventilation should be supplemented by airborne infection controls such as high- efficiency air filters and ultraviolet lights to kill virus particles Avoid overcrowding, particularly on public transport and in public buildings ---------------------------------- WHO assessment: If aerosols prove to be significant factor in pandemic, it could affect current advice on keeping 1-metre of physical distancing. Masks may be needed indoors, even in socially-distant settings ---------------------------------- Sources: Clinical Infectious Diseases, NPR, Reuters, The New York Times © GRAPHIC NEWS Picture: CDC