A couple covered in mud wait for it to dry at the Salt-works lakes near the Black Sea town of Burgas in Bulgaria on July 25, 2019. Thousands of tourists visit the red salt lakes for mud baths, which are believed to help the healing of muscular disorders and rheumatism. (Photo by Nikolay Doychinov/AFP Photo)

LiLou the therapy pig stands in front of a departures board at San Francisco International Airport in San Francisco, California, U.S. October 4, 2019. (Photo by Jane Ross/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 man wearing a traditional Russian costume holds a goose after a traditional goose fight during celebrations of Maslenitsa, also known as Pancake Week, which is a pagan holiday marking the end of winter, in Suzdal, Russia on February 29, 2020. (Photo by Maxim Shemetov/Reuters)

A police officer chases shoppers to clear the streets of the Red Light market on the first day of lockdown to stop the spread of the coronavirus disease (COVID-19) in Monrovia, Liberia on April 11, 2020. (Photo by Derick Snyder/Reuters)

A Palestinian boy dips in a natural spring to cool off during a heat wave, amid concerns about the spread of the coronavirus disease (COVID-19), near Jericho in the Israeli-occupied West Bank on May 17, 2020. (Photo by Mohamad Torokman/Reuters)

The body of one of several U.S. soldiers who were executed after being captured by North Korean troops just south of Seoul in early July 1950. (Photo by AP Photo)

Traders lay out their stools in a fishing village of Long Hai commune in Vung Tau province, Vietnam on June 17, 2020 with the market opening at midnight and trading into the early hours of the morning each day. It is the largest wholesale fishing market in the region and market traders can be seen sorting their fish into their different types before putting them into different coloured boxes for sale. (Photo by Pham Huy Trung/Solent News)