Bird flu may have started in geese, rather than in ducks as scientists had believed. The discovery follows tests on hundreds of birds collected before last year's slaughter of nearly 1.6 million chickens. 'Genetic information suggests [bird flu] was a new introduction from another source, as reflected by the rapid evolutionary change within chickens,' microbiologist Professor Ken Shortridge told the Post. Scientists had thought the virus was passed from ducks to chickens, but had not known how. 'In terms of evolutionary history, ducks are more aquatic than geese. Geese are somewhat in between aquatic ducks and chickens that stick to land. Geese could thus act as an original or an intermediate host for the virus,' Professor Shortridge said. Research on the 1,366 fowl collected shortly before the slaughter of chickens showed two per cent of the ducks and 'a small percentage of geese isolates' had the avian flu, he said. Nearly one-fifth of chickens had the disease, said Professor Shortridge, from the University of Hong Kong, who took part in a study of the virus with the Department of Health, local universities and the US-based Centres for Disease Control. He said the virus had undergone rapid evolution, making it well adapted within chickens. 'The virus load had been building up between April [last year] when the first case took place and December.' It spread to humans through market stalls selling live chickens, ducks and geese. A three-year-old boy died after catching the bird flu in May last year. It was the first time avian flu had been found in a human. A further 17 human cases were reported in November and December, and five of them died. The Department of Health announced yesterday that $55 million would be needed next year to maintain its surveillance programme and poultry import controls against bird flu.