A probe into an outbreak of bird flu at a Hong Kong chicken farm and carcasses popping up in city waters have raised questions over whether the H5N1 virus is going undetected in southern China.
The report released this month said wild birds were the most likely carriers of the virus that broke out in December on a farm close to the territory's border with the southern Chinese province of Guangdong, prompting the culling of 90,000 chickens.
While the authors could not say for certain where in Asia the wild bird may have contracted H5N1, the report said the specific version of the virus was the same as that "currently circulating among poultry in southern China".
The report came days after two dead chickens with H5N1 were found floating in the sea off Hong Kong, the latest of more than a dozen chickens, ducks and other birds to wash up along the city's coastline since the start of year.
"From the various investigations we have done (the washed-up carcasses) are most likely drifting down from the Pearl River," Hong Kong's health secretary York Chow said in early February.
Hong Kong sits at the southern tip of a Guangdong's large Pearl River delta.
Malik Peiris, a virologist at Hong Kong University and one of the world's leading bird flu researchers, said he agreed with Chow's assessment.
"It is not really plausible that they came from Hong Kong," he told AFP.