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)

The waning moon sets behind leafless sumac trees on a crisp, clear morning, Thursday, December 15, 2016, in Portland, Maine. Much of the northern Mid-Atlantic and Northeast will stay cold for the next couple of days as the arctic air remains stuck over the northern Appalachians, the National Weather Service said. (Photo by Robert F. Bukaty/AP Photo)

Passengers hold 500 (bottom) rupee banknotes to buy train tickets at a railway booking counter in Allahabad, India, November 9, 2016. People are queuing up outside banks across India to exchange 500 and 1,000 rupee notes after they were withdrawn as part of anti-corruption measures. Indians will be able to exchange their old notes, which stopped being legal tender at midnight on Tuesday, for new ones at banks until 30 December. The surprise move is part of a government crackdown on corruption and illegal cash holdings. Banks were shut on Wednesday to allow them enough time to stock new notes. There are also limits on cash withdrawals from ATMs. The BBC's Yogita Limaye in Mumbai says there have been chaotic scenes outside many banks. (Photo by Danish Siddiqui/Reuters)

Fans in Star Wars costumes attend the world premiere of Disney's “Star Wars: Rise of Skywalker” at the TCL Chinese Theatre in Hollywood, California on December 16, 2019. (Photo by Valerie Macon/AFP Photo)

People wearing masks and carrying supplies walk past a mannequin wearing a mask in downtown Barcelona, Spain, Saturday, March 14, 2020. Spain's prime minister has announced a two-week state of emergency from Saturday in a bid to contain the new coronavirus outbreak. For most people, the new coronavirus causes only mild or moderate symptoms. For some, it can cause more severe illness, especially in older adults and people with existing health problems. (Photo by Emilio Morenatti/AP Photo)

Rajesh Babu, a police officer, wearing a helmet depicting coronavirus, requests a commuter to stay at home during a 21-day nationwide lockdown to limit the spreading of coronavirus disease (COVID-19), in Chennai, India, March 28, 2020. (Photo by P. Ravikumar/Reuters)

A tourist gets an “Art Hug” from a disinfected costumed man outside the reopened Rijksmuseum in Amsterdam, Netherlands, Monday, June 1, 2020. The government takes a major step to relax the coronavirus lockdown, with bars, restaurants, cinemas and museums reopening under strict conditions. (Photo by Peter Dejong/AP Photo)

Health workers screen residents for COVID-19 symptoms at Dharavi, one of Asia's biggest slums, in Mumbai, India, Monday, August 3, 2020. India is the third hardest-hit country by the pandemic in the world after the United States and Brazil. (Photo by Rafiq Maqbool/AP Photo)