A Kurdish fighter from the People's Protection Units (YPG) fires his rifle at Islamic State militants as he runs across a street in Raqqa, Syria, July 2017. (Photo by Goran Tomasevic/Reuters)

British Prime Minister Boris Johnson visits the Pavegen stand, a company that converts footsteps into energy, at the Innovation Zone during the UK-Africa Investment Summit in London, Britain on January 20, 2020. (Photo by Leon Neal/Pool via Reuters)

A tourist carries her luggage in a flooded St. Mark's Square, in Venice, Wednesday, November 13, 2019. The high-water mark hit 187 centimeters (74 inches) late Tuesday, Nov. 12, 2019, meaning more than 85% of the city was flooded. The highest level ever recorded was 194 centimeters (76 inches) during infamous flooding in 1966. (Photo by Luca Bruno/AP Photo)

A car drives through a flooded road following heavy rain in Gaza City on December 27, 2019. (Photo by Mohammed Abed/AFP Photo)

Race fans watch from the grandstands as Air Force One circles the Daytona International Speedway as President Donald Trump makes his arrival to attend the NASCAR Daytona 500 auto race at Daytona International Speedway, Sunday, February 16, 2020, in Daytona Beach, Fla. (Photo by Jim Topper/AP Photo)

Pedestrians cross a road in Cape Town, South Africa Saturday, March 28, 2020, as South Africa went into a nationwide lockdown for 21 days in an effort to control the spread of the coronavirus. (Photo by Nardus Engelbrecht/AP Photo)

A four-legged robot dog called SPOT patrols a park as it undergoes testing to be deployed as a safe distancing ambassador, following the coronavirus disease (COVID-19) outbreak, in Singapore on May 8, 2020. (Photo by Edgar Su/Reuters)

Chinese epidemic control workers wear protective suits as they disinfect each other after performing nucleic acid swab test for COVID-19 on citizens at a government testing site in Xicheng District during an organized tour on June 24, 2020 in Beijing, China. While Chinese government medical officials have said they believe they have controlled the spread, authorities are trying to contain the outbreak linked to the Xinfadi wholesale food market, Beijing's biggest supplier of produce and meat. (Photo by Kevin Frayer/Getty Images)