Relatives yesterday told an inquest how they watched helplessly as bird flu claimed their loved ones. A leading US scientist said many questions about the virus remain unanswered. Dr Keiji Fukuda, chief of epidemiology at the Centres for Disease Control and Prevention in Georgia, told the opening day of an inquest into the deaths of five people from the H5N1 virus in 1997 that it was still not known how the first victim, aged three, became infected. 'Despite a great deal of investigative work, we were unable to determine specifically how Lam Hoi-ka became infected,' said Dr Fukuda. However, he said the boy was most likely to have contracted the virus from local poultry. 'Usually, avian viruses do not jump from birds to humans. But this particular virus appeared able to do so. We do not understand why. Yet if an avian virus exchanged genes with human influenza, it becomes more easily transmittable from person to person, which is the biggest danger,' he said. Dr Fukuda was invited by the Government to investigate the virus in August 1997. The inquest also heard of the deterioration and deaths of Lok Yuk-fui, 54, and Tse Man-si, 13. Lok's widow, Kwok Choy-wan, gave a tearful account of how her husband fell sick after a trip to Korea in November 1997. 'When he came back on November 29, he had a fever and was admitted to Queen Elizabeth Hospital,' Ms Kwok said. 'The diagnosis was acute pneumonia. His condition deteriorated and he was taken to the intensive care unit, where he died on December 5. I was told that he died of influenza A and only learned from the television that it was the H5N1 bird flu.' Hoi-ka's parents, who did not appear in court, said in a written statement that their son had not been in contact with poultry, but had made a two-day trip to Shenzhen during Lunar New Year. Wong Iok-heng, mother of Man-si, recalled the death of her daughter. 'She was the jewel of my life. . .She first suffered a sore throat and a runny nose, then a fever on November 21,' she said. 'She was admitted to Prince of Wales Hospital on November 26. She appeared to recover the following week but her health deteriorated in early December. 'She was diagnosed with pneumonia . . . and finally fell unconscious and died in the afternoon of December 21.' Dr Fukuda said it was not known whether the virus would surface again. 'At some predictable point in the future, it is extremely likely . . . that another 'new' influenza virus with the potential to cause a pandemic will appear,' he said. 'Though it's out of sight, it should not be out of mind.' The court heard the bird flu was discovered as early as the 1960s in South Africa and first appeared locally in March 1997 when 4,000 chickens died from bird flu on New Territories farms. The bird flu's first victim was Hoi-ka on May 21. It later killed four others, including Lam Shuk-yi, 34, and Teresita Castula, 25, taking the death toll to five. The Government slaughtered 1.2 million chickens to rid Hong Kong of the virus. The inquest continues before Coroner Paul Kelly.