A woman waits at a polio immunisation health centre, in Maiduguri, Borno State, Nigeria, August 29, 2016. Nigeria's military has liberated large swathes of land from Boko Haram but a ride with an army convoy, all guns firing for fear of ambush, shows how far the northeast is from normality after a brutal Islamist insurgency that has displaced millions. (Photo by Afolabi Sotunde/Reuters)

Russian servicemen look on as a Mi-24 helicopter fly overhead during the Open Water competition for pontoon bridge units, as part of the International Army Games 2018, outside Murom, Russia August 3, 2018. (Photo by Maxim Shemetov/Reuters)

Sukhoi Su-30SM jet fighters of the Russkiye Vityazi (Russian Knights) aerobatic team perform during a demonstration flight in Krasnoyarsk, Russia October 6, 2018. (Photo by Ilya Naymushin/Reuters)

A woman throws water at passing motorists during celebrations for the Thingyan festival, also known as the Buddhist New Year, in Naypyidaw, Myanmar on April 16, 2019. (Photo by Thet Aung/AFP Photo)

A masked Bulgarian dancer takes part in the second competition day of the 24th International Festival of Masquerade Games “Surva” in the town of Pernik, Bulgaria Saturday, January 31, 2015. Some 5,000 people are expected to take part in the three-day festival devoted to an ancient Bulgarian pagan rite. Surva is performed by costumed men, some in sheepskin, or other colorful garments, bells and masks, who walk around and dance to scare away the evil spirits, in hope to provide a good harvest, health, fertility, and happiness. (Photo by Valentina Petrova/AP Photo)

A Miniature Dachshund (L) wears a duck bill-shaped dog muzzle while sitting in a stroller with another Miniature Dachshund at the “Interpets” international pet fair in Tokyo, Japan, April 2, 2015. (Photo by Kiyoshi Ota/EPA)

UConn students from Storrs, Conn., Gary Tu, Danny Wang and Victor Zheng, fish at Shenipsit Lake in Tolland, Conn. during sunset on Tuesday, August 19, 2014. (Photo by Jim Michaud/AP Photo/Journal Inquirer)