A new strain of H5N1 bird flu has emerged in China that is poised to start yet another global wave of infection. Nearly three times as many Chinese poultry are infected with H5N1 now than last year, despite ChinaÂ’s insistence that all poultry be vaccinated. In fact, vaccination may be the reason for the increase in infections, researchers say.Yi Guan and colleagues at the University of Hong Kong have been testing poultry in markets across southern China for flu for years, the only such long-term monitoring in the world. Between mid-2004 and mid-2005 they found 0.9% of market poultry were carrying H5N1, including 2% of ducks, a major carrier of the virus.
Between then and June 2006, however, they found it in 2.4% of market poultry on average, a near-threefold increase. It now infects 3.3% of ducks. The team found the virus in chickens during 11 months of the year, up from four previously.