The new coronavirus is likely spreading through the air to some degree, the United States' top infectious disease official has said, one day after the World Health Organisation changed its guidance on the ways the virus spreads.

“Still some question about aerosol but likely some degree of aerosol,” Anthony Fauci, the head of the United States' National Institute of Allergy and Infectious Diseases, said by video during a panel session at a Covid-19 conference organised by the International AIDS Society.