outbreak
Thursday
Tuesday
A measles vaccine, such as the one shown here from a Los Angeles clinic, is highly effective in preventing the spread of measles. Lucy Nicholson/Reuters hide caption
Monday
Scientists say low chlorine levels in Flint's water system during the city's water crisis in 2014 and 2015 led the bacterium Legionella pneumophila to proliferate, causing a deadly outbreak of Legionnaire's disease. Science Source hide caption
Lethal Pneumonia Outbreak Caused By Low Chlorine In Flint Water
Wednesday
Workers spray to kill fleas in a public school in Antananarivo, Madagascar's capital. A bite from an infected flea can spread the plague, which has stricken 157 people in the island nation since August. Anadolu Agency/Getty Images hide caption
Sunday
Tuesday
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
Thursday
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
Thursday
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