Ma Whero from Mischief of Comic Slams collides with Scarface Clawdia of Smash Malice during the Richter City Roller Derby Season Grand Final at TSB Arena on July 21, 2012 in Wellington, New Zealand. Hagen Hopkins/Getty Images hide caption

toggle caption Hagen Hopkins/Getty Images

A colorized scanning electron micrograph showing clumps of methicillin-resistant Staphylococcus aureus bacteria in 2005. Janice Carr; Jeff Hageman/CDC hide caption

toggle caption Janice Carr; Jeff Hageman/CDC