The resurgence of the COVID-19 pandemic in Shanghai had already begun in late February before the city's first case was discovered on March 1, a senior official with the city's Center for Disease Control and Prevention declared on Tuesday.Due to the high-concealing nature of the dominant Omicron variant of the coronavirus, COVID-19 was already being transmitted on a certain scale across the city when the first positive case was detected, Sun Xiaodong, deputy director of the Shanghai CDC, said."\\;The virus then spread rapidly across local wholesale markets, wet markets, companies and other gathering places and sites, triggering a wide range of community transmission in a rather short period of time,"\\; he explained at the city's daily COVID-19 press briefing.