SHANGHAI - China confirmed three more cases of bird flu on Sunday, as authorities sought to curb a deadly outbreak by banning live poultry sales and disinfecting schools. The new cases of the H7N9 strain of avian influenza brought the number recorded in China’s eastern region to 21 since it was announced a week ago that the virus had been found in humans for the first time. Six people have died, including four in Shanghai, which has recorded 10 cases of the disease. Of the three newly confirmed cases, two were elderly men in Shanghai who are receiving treatment, local government said. The third was a 55-year-old man working in the live poultry trade and was reported in Anhui province, according to Xinhua.