The H5N1 bird flu virus found in a 33-year-old man who died last month is similar to that found in his nine-year-old son, but both are different from the 1997 strains that infected humans, the Department of Health said yesterday. A spokesman said the virus genes were purely avian in origin. 'In the absence of human influenza gene segments in the viruses of these two cases, the risk of human-to-human transmission of an H5N1 virus will be low. So there is no cause for panic among members of the public.' He said Hong Kong had a sensitive and comprehensive surveillance system that could detect suspected cases early and prevent them from spreading. The surveillance system had not shown any unusual increases in influenza cases or signs of H5 viruses. But the spokesman warned that people with flu symptoms should seek early medical treatment because March was a peak season for the illness. People should avoid direct contact with poultry and birds and they should wash their hands with soap if they do have contact. The bird flu scare was sparked after the Hong Kong man, surnamed Ko, died six days after developing pneumonia and being admitted to Prince Margaret Hospital on February 11. His nine-year-old son developed fever, a cough and runny nose on February 9 and was admitted to Princess Margaret Hospital on February 12. He has since recovered. The family had visited relatives in Pingtan, a remote island town in eastern Fujian, over the Lunar New Year. Ko's eight-year-old daughter was admitted to a mainland hospital after developing pneumonia on January 28 but died on February 4. The rest of the family returned to Hong Kong on February 10.