A round circle of smoke coming from the mouth of the Etna volcano is seen in the sky during an eruption on the southern Italian island of Sicily April 11, 2013. Mount Etna is Europe's tallest and most active volcano. (Photo by Antonio Parrinello/Reuters)

A visitor looks at a sculpture entitled “Couple Under an Umbrella, 2013” by artist Ron Mueck during the press day for his exhibition at the Fondation Cartier pour l'art contemporain in Paris April 15, 2013. (Photo by Charles Platiau/Reuters)

Migrants ride on top of a northern bound train toward the US-Mexico border in Juchitan, southern Mexico, Monday, April 29, 2013. Migrants crossing Mexico to get to the U.S. have increasingly become targets of criminal gangs who kidnap them to obtain ransom money. (Photo by Eduardo Verdugo/AP Photo)

Corporal of Horse Andy Radford prepares to mount his horse in the parade square at Hyde Park Barracks on April 15, 2011 in London, England. Members of the Household Cavalry gave a behind the scenes tour of many of the duties performed as part of their daily routine, including special preparation ahead of the forthcoming Royal Wedding. The Household Cavalry will perform several ceremonial duties during the summer, including the Royal Wedding on April 29, and the Queen's Birthday Parade (Trooping the Colour) in June. (Photo by Dan Kitwood/Getty Images)

Children of a vendor pose with demon-masks to be hung outside homes believed to ward off negative energy during a government-imposed nationwide lockdown as a preventive measure against the COVID-19 coronavirus, at a roadside stall in Hyderabad, on April 18, 2020. (Photo by Noah Seelam/AFP Photo)

People in face masks cross a near-empty street after the government announced a state of emergency for the capital and some prefectures following the coronavirus disease (COVID-19) outbreak, in Tokyo, Japan on April 16, 2020. (Photo by Kim Kyung-Hoon/Reuters)

An Iraqi medic takes a nasal swab from a woman in Iraq's central shrine city of Najaf on April 20, 2020, during the nationwide lockdown to stem the spread of the novel coronavirus. (Photo by Haidar Hamdani/AFP Photo)

Beesan al-Jubeh, (L), Palestinian under-10 national karate champion, trains with her father Sami (R) and other family members, all wearing face masks and gloves due to the COVID-19 coronavirus pandemic, outside their house in the city of Hebron in the Occupied West Bank on April 9, 2020. (Photo by Hazem Bader/AFP Photo)