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 boy walks past boats docked at the entrance gate of the fishermen's village in the El Max area of the Mediterranean city of Alexandria September 12, 2014. El Max, where hundreds of boats dart through the canals, has been called the “Venice of Egypt” for its waterways and relaxed atmosphere. Its fishermen, however, worry about how they will make ends meet on meagre earnings they say are being reduced further by polluted waters that are making fishing more difficult. While the government has tried to fix the state's bloated finances by cutting subsidies and reining in spending, some argue the reforms hurt Egypt's most vulnerable who have long relied on a generous system of fuel and food subsidies to supplement low incomes. (Photo by Amr Abdallah Dalsh/Reuters)

A model walks the runway wearing creations by Bianca Spender during Mercedes-Benz Fashion Week Australia in Sydney, Australia, 14 May 2018. (Photo by Dan Himbrechts/EPA/EFE)

The northern lights, or aurora borealis, illuminate the sky over Flakstad beach on Lofoten Islands in the Arctic Circle on September 5, 2017. (Photo by Jonathan Nackstrand/AFP Photo)

Border between Sweden and Norway at Moldusen. An approximately 20-meter wide clearing in the forest separates the two Scandinavian nations, consequently cutting Finnskogen in two. Grue Finnskog 2016. (Photo by Terje Abusdal/The Washington Post)

An Exmoor wild goat silhouetted in the sky over the Bristol Channel at the valley of the Rocks, North Devon, as the UK's heat wave continues on July 19, 2018. (Photo by Paul Silver/South West News Service)

Birds sit on the back of a zebra in the Nairobi National Park, near Nairobi, Kenya, November 21, 2018. (Photo by Baz Ratner/Reuters)

A man selling bags of water is seen at a taxi parking bay lined with campaign posters in the district of Lingwala in Kinshasa on December 18, 2018. Democratic Republic of Congo goes to the polls on December 23, 2018 in elections which could see the country emerge from 17 years of conflict-ridden rule under controversial President Joseph Kabila. (Photo by John Wessels/AFP Photo)