The World Health Organization on Tuesday acknowledged “evidence emerging” of the airborne spread of the novel coronavirus, after a group of scientists urged the global body to update its guidance on how the respiratory disease passes between people.

“We have been talking about the possibility of airborne transmission and aerosol transmission as one of the modes of transmission of Covid-19,” Maria Van Kerkhove, technical lead on the Covid-19 pandemic at the WHO, told a news briefing.