In this April 14, 2014 file photo, Hamamatou Harouna, 10, who lost the use of her legs to polio, crawls to the restroom on the grounds of the Catholic Church where she and hundreds of others found refuge after fleeing violence in her village, in Carnot, Central African Republic. Health authorities on Tuesday, August 25, 2020 are expected to declare the African continent free of the wild poliovirus after decades of effort, though cases of vaccine-derived polio are still sparking outbreaks of the paralyzing disease in more than a dozen countries. (Photo by Jerome Delay/AP Photo/File)

People crowd together in an attempt to buy chickens at a Mega-Mercal, a subsidized state-run street market, in Caracas January 24, 2015. President Nicolas Maduro shook up complex currency controls on Wednesday and also prepared Venezuelans for a rise in the world's cheapest fuel prices in response to a recession worsened by plunging oil revenue. The socialist-run OPEC member's economy shrank 2.8 percent in 2014 while inflation topped 64 percent, the socialist leader announced in a speech to parliament, in what is almost certainly the worst performance in Latin America. (Photo by Carlos Garcia Rawlins/Reuters)

People who live in nearby villages make their yearly pilgrimage as they walk up the slopes of the Popocatepetl volcano in Mexico, Wednesday, March 12, 2014. Every year on March 12, residents make their way up the volcano celebrate the day of Don Gregorio Chino Popocatepetl, as the volcano is known to them, with food, music, dance and fireworks. When the sun rises, hundreds of pilgrims head out from the towns of Santiago Xalintzintla, Tlamacas and San Nicolas de Los Ranchos in van and trucks to drive, then walk up the 17,886-foot (5,450-meter) volcano for their daylong celebration. (Photo by Eduardo Verdugo/AP Photo)

This photo taken on April 16, 2014 shows ethnic Kayan women wearing traditional clothes and bronze rings around tbeir neck in Panpet village, Demoso township in Kayah state, eastern Myanmar. Some ethnic Kayan women, also known as Padaung, begin wearing the bronze rings on their neck and legs from a young age. Usually they start wearing six to ten rings when they are five to ten-years-old and then they put on one more ring a year for years after then. (Photo by Ye Aung Thu/AFP Photo)