Hong Kong microbiologist blames 'selfish' mask for Covid-19 cross infection at quarantine hotel

A leading microbiologist in Hong Kong has labelled a face mask as “selfish” because its design contains a valve that filters air being breathed in, but not out. The city's health officials have blamed the mask for a cross infection of Covid-19 at a quarantine hotel, after two guests staying on the same floor tested positive for the disease within a week of each other.