Beijing, Dec 24 (IANS): A human bird flu case has been detected in the Guangdong province in southern China, the country's health authorities said Tuesday.

The patient, a 58-year-old resident of the provincial capital Guangzhou, was under treatment at a local hospital, according to the Guangdong Provincial Health and Family Planning Commission, Xinhua reported.

He was reported to be in a critical condition.

The man tested positive for the H5N6 avian influenza virus during a routine check up for influenza and severe pneumonia, by the provincial health authorities.

Further tests by the Chinese Centre for Disease Control and Prevention confirmed the result Monday.

No abnormal symptoms have ever been found among those who had close contact with the patient so far and experts believe that the infection was limited to an individual case.

In April, a 49-year-old man from southwest China's Sichuan province was confirmed to have contracted the H5N6 virus and died in hospital. The case was believed to be the world's first human H5N6 infection.

Avian influenza, known informally as avian flu or bird flu, refers to influenza caused by viruses adapted to birds.

It has caused a global concern because of its possible transmission to humans and the threat of a pandemic if it mutates to a form that can be easily passed from birds to humans and then, from human to human.