This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)

A person wearing a face mask holds a cat on Swanston Street after cases of the coronavirus were confirmed in Melbourne, Victoria, Australia, January 29, 2020. (Photo by Andrew Kelly/Reuters)

A worker wearing a protective mask uses a blower to remove leafs from a walkway during sunny autumn weather near Stallikon, Switzerland on October 27, 2020. (Photo by Arnd Wiegmann/Reuters)

Drinkers celebrated on the last Friday before Christmas in York, United Kingdom on December 18, 2020. Black Eye Friday, affectionately named for its tendency to prompt drink-fuelled punch ups as the Christmas cheer spills over, has been dampened this year by the global coronavirus pandemic shutting bars and banning socialising. (Photo by Nb press ltd)

A couple is walking hand-held up Kronsberg, just outside Hanover, Germany on April 7, 2020, when the moon rises on the horizon as the so-called supermoon. The moon reaches its perigee, i.e. the point closest to the Earth's orbit, on the night of 7-8 April as a full moon and therefore appears particularly large to the human observer. (Photo by Julian Stratenschulte/dpa via ZUMA Press)

Andreyka, a 10-month-old female bear cub, plays with Rommi, an Alaskan malamute, at the Siberian Zoo in the settlement of Listvyanka, Irkutsk Region, Russia on December 9, 2020. The bear cub, which was found in a weak condition earlier this year, now play-fights with the Alaskan malamute, who adopted her and has seen three generations of bear cubs brought up in the Siberian zoo and released back into the wild. (Photo by Yuri Novikov/Reuters)

South Korean environmental activists wearing masks symbolizing the coronavirus attend a prevention campaign as South Koreans take measures to protect themselves against the spread of coronavirus (COVID-19) on March 30, 2020 in Seoul, South Korea. South Korea has called for expanded public participation in social distancing, as the country witnesses a wave of community spread and imported infections leading to a resurgence in new cases of COVID-19. According to the Korea Center for Disease Control and Prevention on Monday, 78 new cases were reported. The total number of infections in the nation tallies at 9,661. (Photo by Chung Sung-Jun/Getty Images)

Idania Espanola, 63, poses for a photo showing a bra that she will adapt into two face masks, amid the spread of the new coronavirus in Cojimar, Cuba, east of Havana, Tuesday, March 31, 2020. (Photo by Ramon Espinosa/AP Photo)