Two new cases were reported in central China's Henan province and confirmed by the Chinese Center for Disease Control and Prevention, China's official Xinhua news agency reported.
Officials said one of the new patients, a 34-year-old man, was in critical condition. The other patient, a 65-year-old farmer from Zhoukou, was in stable condition after receiving treatment.
Both patients tested positive for the H7N9 bird flu virus Thursday.
Nine others tested positive Saturday for the H7N9 virus -- three in Shanghai, two in eastern China's Jiangsu province, and four in the neighboring Zhejiang province, Xinhua reported.
Shanghai also reported two deaths from the virus Sunday. A 67-year-old woman succumbed to the virus late Saturday and a 77-year-old man died Sunday after testing positive for bird flu, officials said.