The woman, from the Xinjiang Uygur Autonomous Region, in east China, fell ill shortly before visiting a poultry market on January 20, a local health official told Xinhua.
China reported its first bird flu death this year on January 5, when a young woman, 19, from Beijing was diagnosed with the deadly virus and died in hospital. Last Saturday, a 27-year-old woman also died from bird flu and a 16-year-old boy from Hunan, southeast China, died just four days ago.
Doctors said that a two-year-old girl, who was reported to be seriously ill with the virus, is out of danger.
All of the victims had come into contact with poultry before falling ill.
According to the World Health Organization, of the 34 cases confirmed to date in China, 22 have been fatal.
