The World Health Organization urged China on Tuesday to step up testing of wild geese and gulls, as well as humans who’ve come in contact with them near a remote saltwater lake where 5,000 birds have died. The birds might spread avian flu when they fly south this summer, the WHO warned. Officials say 54 people have died in Asia so far this year after becoming infected by sick birds — although none in China. Health officials worry the bird flu might mutate into a form that could spread directly from person to person, setting off a pandemic. Full Story