FILE - This April 8, 2013 file photo shows a worker cleaning empty cages used for transporting chickens, to prevent an outbreak of H7N9 infections at a wholesale poultry market in Hong Kong. Scientists who sparked an outcry by creating easier-to-spread versions of the bird flu want to try such experiments again using a worrisome new strain. Since it broke out in China in March, the H7N9 bird flu has infected more than 130 people and killed 43. Leading flu researchers say that genetically engineering this virus in the lab could help track whether it�s changing in the wild to become a bigger threat. They announced the pending plans Wednesday in letters to the journals Science and Nature.
Section:Photo
