School boys who attend Sri Lankan traditional dance training wait for their graduation ceremony at a Buddhist temple in Colombo, Sri Lanka January 23, 2017. (Photo by Dinuka Liyanawatte/Reuters)

Paramedics carry an injured woman out from a subway station after a rush-hour subway train derailment, to be transported by a medical helicopter in Moscow, Russia, on Tuesday, July 15, 2014. A rush-hour subway train derailed in Moscow Tuesday, killing 20 people and injuring at least 150, emergency officials said. Several cars left the track in the tunnel after a power surge triggered an alarm, which caused the train to stop abruptly. (Photo by Ivan Sekretarev/AP Photo)

A feeder trains a Siberian tiger cub at Erdaohe Tiger Park July 2, 2006 in Antu County of Yanbian Chaoxian Autonomous Prefecture, Jilin Province, China. About 15 artificially-fed Siberian tigers from Harbin Siberian Tiger Park are being trained to develop their ability to live in the wild. The wild Siberian tiger is listed as one of the most endangered species in the world, with its existing number estimated at around 400 worldwide, mainly in the northeastern part of China and the Far East of Russia. Reportedly there are more than 1,300 Siberian tigers which have been raised in China. (Photo by China Photos/Getty Images)

Young girls practice acrobatic skills in the Sichuan Provincial Art School July 14, 2008 in Chengdu of Sichuan Province, China. (Photo by China Photos/Getty Images)

Weakened by sickness and malnutrition, Arbty Mohammad, 2, lies in the Banadir Hospital on August 12, 2011 in Mogadishu, Somalia. Some 100,000 Somalis have flooded into Mogadishu from drought and famine stricken areas of the country. The UN warned Friday that a cholera epidemic could spread through Mogadishu, as Somalis fill unsanitary makeshift camps throughout the capital. (Photo by John Moore/Getty Images)

Christian families living in a refugee camp stand under a tree in Kaga-Bandoro, Central African Republic, Tuesday February 16, 2016. Refugees in the north of Central African Republic say they hope the new president will bring peace but no one is heading home just yet. Thousands are still living in displacement camps in Kaga-Bandoro, a stronghold of the former Muslim rebel group known as Seleka that was in power for nearly a year. The one-time rebels say they are waiting to see how the election turns out before taking any action. (Photo by Jerome Delay/AP Photo)

A Sudanese man walks to a United Nations displacement camp after crossing into Tunisia from Libya on March 06, 2011 in Ras Jdir, Tunisia. As fighting continues in and around the Libyan capital of Tripoli, tens of thousands of guest workers from Egypt, Tunisia, Bangladesh and other countries are fleeing to the border of Tunisia to escape the violence. The situation has turned into a humanitarian emergency as fledgling Tunisia is overwhelmed with the workers. Libyan leader Muammar Gaddafi has vowed to fight to the end. (Photo by Spencer Platt/Getty Images). RAS JDIR, TUNISIA – MARCH 06 2011

Sudanese refugees living in Tel Aviv dance as they celebrate independence from the Republic of Sudan on July 10, 2011 in Tel Aviv, Israel. Israel's Prime Minister Benjamin Netanyahu announced that Israel recognizes the Republic of South Sudan as independent state. South Sudan became a state on July 9 after it separated from the north, with its capital in Juba, following a vote for independence. The country was recognized on July 8 by the government of Sudan. (Photo by Uriel Sinai/Getty Images)