A large majority of Shanghai's recent new local COVID-19 and asymptomatic cases were found among those who were already under quarantine, a positive sign for the city's arduous fight against the pandemic, according to Shanghai's top coronavirus expert.The proportion of new positive cases found during the massive "\\;grid screening"\\; is gradually declining, accounting for only about 10 percent of the total new daily cases, Dr Zhang Wenhong, head of Shanghai's COVID-19 treatment team and director of the National Center for Infectious Diseases, stated on Thursday.It means the community-level transmission has been gradually brought under control, he said on his Weibo social media account on early Thursday morning.