West Nile virus has been making headlines all summer, but the human toll of the disease is far smaller than its impact on bird species. Since West Nile was first spotted in a crow three years ago, at least 111 species have been hit, including the bald eagle and the endangered Mississippi sandhill crane. The spread of the virus is particularly alarming in its rapidity; last year, scientists spotted the affliction in only about a dozen species. This year, hundreds of birds of prey have died in the Upper Midwest, with red-tailed hawks and great horned owls the hardest hit. Wildlife biologists and conservationists are particularly concerned about endangered species, whose tiny populations often cannot survive even a few extra deaths, let alone a major die-off. An already-approved horse vaccine is being tested on birds, but in the meantime, new species continue to turn up with West Nile. “We don’t know of any birds that can’t be affected by the virus,” said Kathryn Converse, a wildlife disease specialist with the U.S. Geological Survey’s National Wildlife Health Center.