HK begins mass cull of birds at market, screens virus

HONG KONG -- Health workers in masks culled tens of thousands of chickens in Hong Kong on Wednesday, a day after authorities raised the bird flu alert level to “serious” following a H5 bird flu outbreak at a farmThe outbreak near the border with China was the city’s first in five years despite mass vaccination of the birds, prompting concerns that the virus might have mutated. “Viruses change and since 1997, it has been changing. If we have been using the same vaccine since 2003, its efficacy would not be the same,” Ho Pak-leung, a microbiologist at the University of Hong Kong, told Reuters in an interview.