The latest human cases of bird flu in China appeared to be isolated events with no other people affected and no reported outbreak of the disease among poultry, the government said Monday.

A 24-year-old man in eastern Jiangsu province died from bird flu on December 2, and authorities announced on Friday last week that his father also had the H5N1 strain of the virus, raising fears of human-to-human transmission.

Health ministry spokesman Mao Qun'an told reporters on Monday the father, surnamed Lu, 52, was recovering from the virus and that there was no evidence the man had contracted the disease from his son.

"There is no biological basis for (the theory of) human-to-human transmission," Mao said.

The H5N1 strain has passed from human to human only in very rare cases and scientists fear that such a transmission could become more efficient and widespread through mutation, causing a global pandemic.

Mao said the strain that killed the son had not mutated from H5N1.

He said 34 people who had close contact with the father and the son were being kept under observation but none of them had shown symptoms of the disease.

There is no report of bird flu outbreaks among poultry in Jiangsu province either, he added.

This followed a familiar pattern in China where humans have contracted the disease in an area where there have been no reported outbreaks among poultry.

The father-son case has brought reports of human cases of bird flu in China to 27 since 2003. Seventeen of those people have died.