Shanghai health authorities issued an ominous warning to the city’s 25 million residents that visiting crowded areas could lead to a resurgence of Covid-19 , after six new community infections came to light on Friday. “We want to urge the residents again to avoid crowding,” Zhao Dandan, deputy Shanghai health commissioner told a press briefing. “Please refrain from going to public venues that are densely crowded without good ventilation systems.” The total number of cases spotted in communities since Shanghai lifted a citywide lockdown on June 1 rose to 32, with dozens of residential compounds classified as “medium risk zones” in which people must be confined to their homes for 14 days. The scattered cases heightened worries about a resurgence of the coronavirus in mainland China’s commercial hub, which recently emerged from a two-month shutdown. At least 14 million residents in seven of the city’s 16 districts will be required to undergo nucleic acid tests on Saturday as the municipal government strengthens virus control amid rising cases. Shanghai has detected 118 Covid-19 carriers since lockdown ended, a drop in the ocean compared to the total caseload of about 626,600 between March 1 and May 31. But a rising number of infections found outside quarantined areas increases the risk of a sporadic spread of the virus after companies and retailers resumed operations to get the ailing local economy back on track. “The 32 cases in communities could spread quickly and lead to an explosive growth in the number of new infections within just a few days if they were not spotted promptly,” said Meng Tianying, a senior executive at Shanghai-based consultancy Domo Medical. “City officials are still wary of hidden transmission chains and feel it necessary to conduct mass testing to screen for new infections in the populous districts.” On Thursday, the local health commission announced that three employees at a popular beauty salon in the city’s downtown Xuhui district were found to have caught the virus. This has triggered a campaign to track and trace some 502 customers from 15 districts known to have visited the premises in the previous eight days. Two more cases involving people who had visited a Suning home appliance store in northeastern Yangpu district also carried the risk of widespread transmission since they had come into contact with hundreds of shoppers, Zhao told Friday’s briefing. Pudong New Area, east of Shanghai’s Huangpu River, home to Tesla’s Gigafactory and the mainland’s largest equity trading bourse, the Shanghai Stock Exchange, has told all of its 5.7 million residents to undergo Covid-19 tests on Saturday. Other administrative regions in the city centre, including Xuhui and Hongkou districts, plan to test all their residents on Saturday too. Local authorities said the mass testing exercise was part of “normal” virus controls. Shanghai municipality said in late May that the citywide lockdown would be relaxed in a “phased” manner to gradually return businesses and life to normality by late June. Shanghai Disney Resort reopened partially on Friday following an 81-day shutdown because of the disease outbreak. The 400,000 square-metre Wishing Star Park, Blue Sky Boulevard and World of Disney Store resumed operations today with limited capacity and reduced opening hours. Shanghai Disney said on Thursday that its team was preparing to reopen the entire resort. The Disneyland amusement park, Disneytown and two resort hotels will remain closed until further notice.