People hold smartphones while walking past QR codes for the LeaveHomeSafe Covid-19 contact-tracing app posted outside the Central Government Offices in Hong Kong, China, on Thursday, Feb. 4, 2021. The Asian financial hub has been attempting to curb a fourth wave of Covid-19 infections with targeted lockdowns that have seen authorities cordon off an area and restrict movement until residents receive negative results. Photographer: Paul Yeung/Bloomberg via Getty Images
