Hong Kong authorities have placed a public housing block under a three-day restriction order for more than 2,500 residents to undergo daily Covid-19 testing, after a suspected Omicron superspreader was believed to have infected 16 others in the building. The order, which takes effect on Friday, was issued after top microbiologist Professor Yuen Kwok-yung inspected Kwai Chung Estate’s Yat Kwai.