A man carries old plastic containers in March 2012 through the Kibera slum in Nairobi, Kenya. Kenyans living in poverty often collect plastics that they can turn into cash by taking it to companies that recycle it. Carl de Souza/AFP/Getty Images hide caption

itoggle caption Carl de Souza/AFP/Getty Images

Lyme disease is spread by deer ticks like this one. A study finds that some people can be reinfected many times with the bacteria that cause the disease. Lauree Feldman/Getty Creative Images hide caption

itoggle caption Lauree Feldman/Getty Creative Images