A second human case of bird flu has been identified in under a week in Vietnam where 36 people have died from the disease since late 2003, a health official said.

A 58-year-old man from northern Vietnam´s Thanh Hoa province was admitted to the Institute of Tropical Diseases in Hanoi late last week and tested positive to the H5N1 virus, said Cao Van Vien, deputy director of the institute.

"He was transferred to our hospital from the tuberculosis institute," Vien told AFP.

Doctors said the patient and another 52-year-old man from Vinh Phuc province, also in the north, who too tested positive to the virus in the same institute late last week, were in stable condition.

"We are now treating two H5N1 patients and they are in good condition," one of the doctors said.

Health officials in the two provinces said they had quarantined the patients´ houses.

"We are investigating the source of infection for the man from Thanh Hoa province," an official from the provincial preventive health care centre said.

The Hanoi institute had held a ceremony on Friday to discharge a 21-year-old H5N1 patient, who had been in a critical condition and whose close relatives too were infected with the deadly virus in February.