In this photograph taken on February 18, 2016, Pakistani children ride on swings in the predominantly Pashtun Korangi District of Karachi. In a rundown district of Karachi, Rabia balks at a neighbour's proposal to vaccinate her children, demonstrating one of the biggest hurdles to eradicating polio in Pakistan by the end of the year: confused and frightened parents. (Photo by Asif Hassan/AFP Photo)

A woman holds a hedgehog at the Harry hedgehog cafe in Tokyo, Japan, April 5, 2016. In a new animal-themed cafe, 20 to 30 hedgehogs of different breeds scrabble and snooze in glass tanks in Tokyo's Roppongi entertainment district. Customers have been queuing to play with the prickly mammals, which have long been sold in Japan as pets. The cafe's name Harry alludes to the Japanese word for hedgehog, harinezumi. (Photo by Thomas Peter/Reuters)

A reveller reacts during a water fight at Songkran Festival celebrations in Bangkok April 13, 2016. The three-day Songkran Festival starts on 13-15 April annually and is celebrated with splashing water and putting powder on each others faces as a symbolic sign of cleansing and washing away the sins from the old year. (Photo by Jorge Silva/Reuters)

A man looks at a mural painted on the walls of houses in Zaraeeb, created by French-Tunisian artist El Seed, in the shanty area known also as Zabaleen or “Garbage City” on the Mokattam Hills in eastern Cairo, Egypt, April 4, 2016. (Photo by Amr Abdallah Dalsh/Reuters)

Matachines dancers participate in a religious festival in Saltillo, Mexico, April 17, 2016. Matachines dancing is a masked dance introduced by Spanish missionaries, and has been adopted by cultures from Peru to northern Mexico. It is performed to show respect to Mother Mary or the Guadalupe Virgin, a saint, or to simply worship God. (Photo by Daniel Becerril/Reuters)

Britain's Prince Harry meets Chewbacca during a visit to the Star Wars film set at Pinewood Studios near Iver Heath, west of London, Britain, April 19, 2016. Prince William and Prince Harry are touring Pinewood to visit the production workshops and meet the creative teams working behind the scenes on the Star Wars films. (Photo by Adrian Dennis/Reuters)

A girl calls to her mom as she stands near a dead whale on the shore Monday morning, April 25, 2016, on the cobblestone beach at Lower Trestles on San Onofre State Beach, just south of San Clemente, Calif. (Photo by Jeff Gritchen/The Orange County Register via AP Photo)

People carry drinks at 80s Bar in Damascus, Syria, March 11, 2016. In Damascus's Old City, just a mile from the battered frontline between government and rebel-held territory, young Syrians smoke, drink beer or soft drinks, and talk about anything but the war. The revival of activity in this once-vibrant quarter is part of efforts to project an air of normality in the Syrian capital, even as the five-year-old war that has killed more than 250,000 people and created 5 million refugees continues to rage nearby. (Photo by Omar Sanadiki/Reuters)