A helicopter drops fire retardent to protect a property in Balmoral, 150 kilometres southwest of Sydney on December 19, 2019. A state of emergency was declared in Australia's most populated region on December 19, as a record heat wave fanned unprecedented bushfires. (Photo by Peter Parks/AFP Photo)

A child jumps to touch lanterns hung on a tree ahead of the Chinese Lunar New Year celebrations in Beijing on Thursday, January 16, 2020. The world's largest annual migration begins this week in China with millions of Chinese traveling to their hometowns to celebrate the Lunar New Year on Jan. 25 this year which marks the Year of the Rat on the Chinese zodiac. (Photo by Ng Han Guan/AP Photo)

A model presents a creation by designer Alexis Mabille as part of his Haute Couture Spring/Summer 2020 collection show in Paris, France, January 21, 2020. (Photo by Francois Lenoir/Reuters)

People wear masks to help guard against the Coronavirus in downtown Tehran, Iran, Sunday, February 23, 2020. On Sunday Iran's health ministry raised the death toll from the new virus to 8 people in the country, amid concerns that clusters there, as well as in Italy and South Korea, could signal a serious new stage in its global spread. (Photo by Ebrahim Noroozi/AP Photo)

U.S. President Donald Trump holds news conference on the coronavirus outbreak at the White House in Washington, U.S., February 26, 2020. (Photo by Carlos Barria/Reuters)

Shanghai Ballet dancers wearing masks practise in a dance studio in Shanghai, China, as the country is hit by an outbreak of the novel coronavirus, February 20, 2020. (Photo by Aly Song/Reuters)

Protesters wear gas masks in the front of the Romanian Environment Ministry in Bucharest March 4, 2019, to demand better air. Dozens of people holding placards reading “Our children don't breath air anymore” gather in the front of the Environment Ministry to ask for better breathable air in Bucharest. (Photo by Daniel Mihailescu/AFP Photo)

Rachel Miner, 15, left, of Emmetsburg, Iowa, sits with Carlotta Haas, 15, a foreign exchange student from Duesseldorf, Germany, who had been living with Miner and her family but was called home, as they waited for her flight Wednesday, March 25, 2020, in at Minneapolis-St. Paul International Airport in Minneapolis. (Photo by Anthony Souffle/Star Tribune via AP Photo)