A farmer has died of bird flu in far western China, the 14th person to die of the disease in the country.

The Health Ministry confirmed the 62-year-old farmer in the Xinjiang region died July 12 of the H5N1 strain of bird flu, the official Xinhua News Agency said. The case brings China's total number of human bird flu infections to 21, Xinhua said.

The tally includes a case the government confirmed last week occurred in 2003, two years before China publicly acknowledged its first human infection. The 2003 case, disclosed by Chinese researchers in June in a letter to the New England Journal of Medicine , raised questions about Beijing's ability to detect emerging diseases.

The H5N1 virus has killed at least 138 people worldwide since it began ravaging Asian poultry stocks in late 2003, according to a tally kept by the World Health Organization. Most human cases have been traced to contact with infected birds, but experts fear the virus — which remains hard for people to catch — could mutate into a form that spreads easily among people, potentially sparking a pandemic.