Ali Maow Maalin said he avoided getting the smallpox vaccine as a young man because he was afraid of needles. He didn't want others to make the same mistake with polio. Courtesy of the World Health Organization hide caption

itoggle caption Courtesy of the World Health Organization

A newspaper headline calls for the defeat of Zimbabwean President Robert Mugabe on the eve of elections in Zimbabwe on Tuesday in Harare. AP hide caption

itoggle caption AP

Zimbabwe's President Robert Mugabe (left) greets South African President Nelson Mandela in Harare, Zimbabwe, in 1998. The two men have shaped their countries in dramatically different ways. Rob Cooper/AP hide caption

itoggle caption Rob Cooper/AP

An Egyptian man mourns the death of a relative, shot dead after violence erupted Friday night, inside the Muslim Brotherhood field hospital in Cairo. Florian Plaucheur/AFP/Getty Images hide caption

itoggle caption Florian Plaucheur/AFP/Getty Images

Muslim Brotherhood supporters of ousted President Mohammed Morsi attend a protest near Rabaa al-Adawiya mosque in Cairo on Friday. Mohammed Saber/EPA/Landov hide caption

itoggle caption Mohammed Saber/EPA/Landov