Bulgarian men dance in the icy waters of the Tundzha river during a celebration to commemorate Epiphany Day in the town of Kalofer January 6, 2015. It is believed that the ritual will bring good health to the participants throughout the new year. (Photo by Stoyan Nenov/Reuters)

A girl holds her brother in her arm as black smoke rises after an oil well set on fire in the center of al-Kayyara town to the south of Daesh terror organization-held Mosul in Iraq on October 25, 2016. The oil well in the center of al-Kayyara town, which was set alight by retreating Daesh militants in advance of the Iraqi army's takeover of the town on August 24, 2016 has still not entirely been put out. The raw petrol which is still alight is creating black clouds above the city. The residents and wildlife beneath this polluting smoke cloud may find their health at risk. The effects of the fire in the town center on unprotected civilians' health can easily be seen on the hands and faces of children playing on the street. (Photo by dris Okuducu/Anadolu Agency/Getty Images)

A vintage military aircraft is seen parked ahead of the International Air and Space Fair (FIDAE) at the Arturo Merino Benitez international airport in Santiago, Chile March 29, 2016. (Photo by Rodrigo Garrido/Reuters)

Members of the Loktev Ensemble perform during the opening of the 18th Moscow Meets Friends International Festival at the Moscow International House of Music in Moscow, Russia on May 18, 2021. (Photo by Artyom Geodakyan/TASS)

Children surround a man, left, that fell down while walking on a street suspected of having contracted the Ebola virus in the city of Monrovia, Liberia, Tuesday, August 19, 2014. The World Health Organization says the outbreak has killed more than 1,200 people, while authorities struggle to contain its spread and treat the sick. (Photo by Abbas Dulleh/AP Photo)

An Iranian woman wearing a face mask walks on a street in Tehran, Iran, 19 October 2020. According to the Iranian Health ministry, Iran reported its highest daily COVID-19 death toll of 337 and 4,251 new infections in past 24 hours as it appears that Iran is in a third wave of COVID-19 outbreak. (Photo by Abedin Taherkenareh/EPA/EFE)

Health workers watch as the vaccine against the Coronavirus arrives at a nursing home in l'Hospitalet de Llobregat in Barcelona, Spain, on Sunday, December 27, 2020. The first shipments of coronavirus vaccines developed by BioNTech and Pfizer have arrived across the European Union, authorities started to vaccinate the most vulnerable people in a coordinated effort on Sunday. (Photo by Emilio Morenatti/AP Photo)

A vegetable vendor wearing gloves and face mask as a precaution against the coronavirus interacts with a customer in Bengaluru, India, Sunday, October 11, 2020. India's confirmed coronavirus toll crossed 7 million on Sunday with a number of new cases dipping in recent weeks, even as health experts warn of mask and distancing fatigue setting in. (Photo by Aijaz Rahi/AP Photo)