The patient, surnamed Jiang, is a migrant worker in Shenzhen City showed symptoms of fever and pneumonia on June 3 and has been hospitalised. He is now in critical condition, the Health Ministry said in a report.
Medical tests have found Jiang had been to a local market, where live poultry were sold, several times before developing the symptoms.
Jiang's samples tested H5N1 positive by the Shenzhen Center for Disease Control and Prevention and the provincial and national CDCs, the ministry said.
Jiang was reported by the local health authorities as a suspected case of bird flu on Tuesday. All 98 people who had close contact with Jiang tested clear of the disease, the local health bureau said.
This is the 19th human case of bird flu reported in China. Among the previous 18 cases, 12 have died.