Last month, two dead birds tested positive for the H5N1 virus, prompting Hong Kong authorities to kill some 20,000 more birds; now two more cases have been discovered. Two dead black-headed gulls—frequent winter visitors to the area and discovered separately—were found to have had the disease, fueling new concern over its spread, the AP reports. The new cases follow China's first human death from the disease in more than a year.
H5N1 rarely infects humans and usually only strikes those who come into close contact with diseased poultry. The World Health Organization says globally there have been 336 human deaths from 573 confirmed bird flu cases since 2003.