Chinese authorities have extended their lockdown of Shanghai to cover all its 25 million people after a fresh surge in Covid cases. Initially, there had been separate measures for the eastern and western sides, but the whole city is now subject to indefinite restrictions. Shanghai is the largest single city to be locked down to date. The important financial hub has battled a new wave of coronavirus infections for more than a month. Reported cases have risen to more than 13,000 a day, although the numbers are not high by some international standards.