A farm in Iowa plans to slaughter more than five million chickens in response to an outbreak of bird flu. Charlie Neibergall/AP hide caption
outbreak outbreak
Kenyan health officials take the temperatures of passengers arriving at the Nairobi airport on Thursday. Kenya has no reported cases of Ebola, but it's a transportation hub and so is on alert. Simon Maina/AFP/Getty Images hide caption
Developing a vaccine for meningitis B was tricky. Even the existing vaccine doesn't protect against all B strains. Josef Muellek/iStockphoto.com hide caption