Delivery trucks may have provided the source of the new bird flu strain, according to researchers.
Cross-contamination which allowed different viruses to mix and mutate into the new H5N1 strain could have occurred if trucks were not cleaned thoroughly after separately carrying geese, ducks and chickens, said Professor Yuen Kwok-yung, a member of the Government's flu committee and chairman of the infectious diseases division at the University of Hong Kong.
Mainland chickens might have provided the precursor of the H5N1 strain, before it changed into both the new strain and that responsible for the 1997 bird flu outbreak.
On Saturday, Secretary for Environment and Food Lily Yam Kwan Pui-ying said: 'In the transportation process, even in the atmosphere and in the environment and on birds, there is always this possibility that these viruses will be lodged.'
Since the 1997 outbreak, which killed six people, chickens have been segregated from ducks and geese, which can carry the virus without falling ill.
Geese and ducks are slaughtered at the Western Wholesale Food Market before being sold chilled. Chickens, quail, partridges and pigeons are kept at Cheung Sha Wan wholesale market before being transported live to wet markets.
