Experts yesterday expressed concern that the return of the human form of H5N1 flu means the strain may have found a faster way of mutating to cross the species barrier.
If this is so, H5N1 could be a potential pandemic strain, some experts said.
While initial genetic analysis showed that the latest strain was a pure avian flu virus, some said answers needed to be found quickly on how and why the boy who went to Fujian province had become infected.
'The question is how was it transmitted? Were the family members all exposed to one source?' one international expert asked.
Another said the boy probably became infected while in Fujian.
University of Hong Kong virologists said the internal genes of the H5N1 virus found in the boy did not have a 'human flu component', pointing to a pure avian flu.
Legislator Lo Wing-lok, who represents the medical sector, said this meant the virus' behaviour would be similar to the 1997 H5N1 that jumped from a bird directly to a man, and therefore could not efficiently transmit from man to man.
