A medical specialist wearing protective gear accompanies a woman wearing an oxygen mask outside a hospital for patients infected with the coronavirus disease (COVID-19) on the outskirts of Moscow, Russia April 21, 2020. REUTERS/Tatyana Makeyeva

An oxygen mask lays on a bed as a resident is seen in a background at the house for elderly Residence Christalain during coronavirus disease (COVID-19) outbreak, in the Brussels commune of Jette, Belgium April 13, 2020. REUTERS/Yves Herman

People wearing face masks wait with oxygen tanks at a private distributor that recharges tanks, amid the spread of the coronavirus disease (COVID-19), in Guayaquil, Ecuador April 9, 2020. REUTERS/Vicente Gaibor del Pino

A man in a face mask waits with an oxygen tank at a private distributor that recharges tanks, amid the spread of the coronavirus disease (COVID-19), in Guayaquil, Ecuador April 9, 2020. REUTERS/Vicente Gaibor del Pino

A doctor wearing a face mask adjusts oxygen devices at a newly opened quarantine centre, following the outbreak of coronavirus disease (COVID-19), in Misrata, Libya March 30, 2020. Picture taken March 30, 2020. REUTERS/Ayman Al-Sahili

Healthcare workers wearing protective face masks bring oxygen bottles to the emergency unit at 12 de Octubre Hospital, amid the coronavirus disease (COVID-19) outbreak in Madrid, Spain March 30, 2020. REUTERS/Juan Medina

A man from a Bellevue Healthcare van wheels in oxygen tanks while wearing a mask and gloves at Aegis Living at Marymoor, an assisted living facility linked to several cases of coronavirus, during the coronavirus disease (COVID-19) outbreak in Redmond, Washington, U.S. March 21, 2020. REUTERS/Lindsey Wasson

Dec 28, 2019; Glendale, AZ, USA; Clemson Tigers quarterback Trevor Lawrence (16) breathes oxygen with a mask on the sidelines against the Ohio State Buckeyes in the 2019 Fiesta Bowl college football playoff semifinal game at State Farm Stadium. Mandatory Credit: Mark J. Rebilas-USA TODAY Sports

A participant wearing a costume attends a Halloween party at a village in Bangkok, Thailand, October 31, 2019. REUTERS/Athit Perawongmetha

Firefighters battle the Woolsey Fire as it continues to burn in Malibu, California, U.S., November 11, 2018. REUTERS/Eric Thayer TPX IMAGES OF THE DAY

Participants parade through the town during the annual Bonfire Night festivities in Lewes, Britain, November 5, 2018. REUTERS/Toby Melville

QUALITY REPEAT - Susan Williams puts on her oxygen mask in her rocking chair in her living room with no wall after she rode out the hurricane in her home following Hurricane Michael in Mexico Beach, Florida, U.S., October 12, 2018. REUTERS/Carlo Allegri

Susan Williams puts on her oxygen mask in her rocking chair in her living room with no wall after she rode out the hurricane in her home following Hurricane Michael in Mexico Beach, Florida, U.S., October 12, 2018. REUTERS/Carlo Allegri

Belarusian hunters cut a killed elk as they take part in the hunting of wild ungulates near the village of Myshanka, Belarus October 6, 2018. Picture taken October 6, 2018. REUTERS/Vasily Fedosenko TPX IMAGES OF THE DAY

Soccer Football - UEFA Nations League - League A - Group 4 - England v Spain - Wembley Stadium, London, Britain - September 8, 2018 England's Luke Shaw is stretchered off the pitch wearing an oxygen mask after sustaining an injury Action Images via Reuters/John Sibley

A Palestinian demonstrator uses a sling to hurl back a tear gas canister fired by Israeli troops during clashes at a protest against Israeli land seizures for Jewish settlements, in the village of Ras Karkar, near Ramallah in the occupied West Bank September 4, 2018. REUTERS/Mohamad Torokman

Participants dance in costumes during the West Indian-American Carnival Day Parade in the Brooklyn borough of New York, U.S., September 3, 2018. REUTERS/Gabriela Bhaskar

A Palestinian demonstrator looks on as he takes cover during clashes with Israeli troops at a protest near the Jewish settlement of Qadomem, in village of Kofr Qadom near Nablus in the occupied West Bank August 17, 2018. REUTERS/Mohamad Torokman

A firefighter wears a flame resistant uniform as wildfire burns in the town of Rafina, near Athens, Greece, July 23, 2018. REUTERS/Costas Baltas

A volunteer work to extinguish wildfires near the Paranoa neighbourhood in Brasilia, Brazil, July 20, 2018. REUTERS/Ueslei Marcelino

Participants gather for the annual May bank holiday "Jack In The Green" parade and festival in Hastings, Britain, May 7, 2018. REUTERS/Toby Melville

A participant takes part in the annual May bank holiday "Jack In The Green" parade and festival in Hastings, Britain, May 7, 2018. REUTERS/Toby Melville

A participant takes part in the annual May bank holiday "Jack In The Green" parade and festival in Hastings, Britain, May 7, 2018. REUTERS/Toby Melville

A participant takes part in the annual May bank holiday "Jack In The Green" parade and festival in Hastings, Britain, May 7, 2018. REUTERS/Toby Melville

A woman strokes a donkey before the procession of the "Virgem da Atalaia" during Holy Week in Alcochete, near Lisbon, Portugal April 1, 2018. REUTERS/Rafael Marchante

A donkey is prepared before the procession of the "Virgem da Atalaia" during Holy Week in Alcochete, near Lisbon, Portugal April 1, 2018. REUTERS/Rafael Marchante

Boxing - Alexander Povetkin vs David Price - WBA Inter-Continental & WBO International Heavyweight Titles - Principality Stadium, Cardiff, Britain - March 31, 2018 David Price wears an oxygen mask after losing the fight Action Images via Reuters/Andrew Couldridge

Penitents take part in the procession of the Santo Sepulcro in La Paz, Bolivia, March 30, 2018. REUTERS/David Mercado

Penitents take part in the Procession del Nazareno as Easter processions take place throughout Spain during Holy Week, in Bilbao, Spain March 26, 2018. REUTERS/Vincent West

A participant wearing a costume prepares for the 40th anniversary of the Sydney Gay and Lesbian Mardi Gras Parade in central Sydney, Australia, March 3, 2018. REUTERS/David Gray

Ultra-Orthodox Jewish boys run across street in costume during the Jewish holiday of Purim in the Williamsburg section of Brooklyn, New York, U.S., March 1, 2018. REUTERS/Shannon Stapleton

A Palestinian demonstrator returns a tear gas canister fired by Israeli troops during clashes near Ramallah, in the occupied West Bank February 16, 2018. REUTERS/Mohamad Torokman

A masked man wearing a Basque beret takes part in carnival celebrations in Alsasua, Spain, February 13, 2018. REUTERS/Vincent West

Revellers wear masks during the traditional Buso Carnival in Mohacs, Hungary, February 11, 2018. REUTERS/Bernadett Szabo

A reveller wearing a mask dances near a bonfire during the traditional Buso Carnival in Mohacs, Hungary, February 11, 2018. REUTERS/Bernadett Szabo

A tamed golden eagle wearing a hood, locally known as tomaga, with silver decorations is seen during an annual hunters competition at Almaty hippodrome, Kazakhstan February 9, 2018. REUTERS/Shamil Zhumatov

A masked reveller poses during the Venice Carnival in Venice, Italy, February 4, 2018. REUTERS/Manuel Silvestri

A masked reveller poses during the Venice Carnival, Italy, February 4, 2018. REUTERS/Manuel Silvestri

A man breathes through an oxygen mask at a medical center in Douma, Eastern Ghouta in Damascus, Syria January 22, 2018. REUTERS/Bassam Khabieh TPX IMAGES OF THE DAY

A man breathes through an oxygen mask at a medical center in Douma, Eastern Ghouta in Damascus, Syria January 22, 2018. REUTERS/Bassam Khabieh

Revellers dressed as devils walk among fireworks during "Correfocs" (fire runs), traditional celebrations in eastern Spain with people dressed as dancing devils while lighting fireworks among crowds of spectators, to mark the end of the local festivities in Palma de Mallorca, Spain, January 21, 2018. REUTERS/Enrique Calvo TPX IMAGES OF THE DAY

Revellers dressed as devils walk among fireworks during "Correfocs" (fire runs), traditional celebrations in eastern Spain with people dressed as dancing devils while lighting fireworks among crowds of spectators, to mark the end of the local festivities in Palma de Mallorca, Spain, January 21, 2018. REUTERS/Enrique Calvo

A Turkey-backed Free Syrian Army fighter is seen near Menagh, Syria January 21, 2018. REUTERS/Osman Orsal

Members of the demining team of the Libyan National Army search for mines, in Benghazi, Libya January 14, 2018. Picture taken January 14, 2018. REUTERS/Ayman Alwrfaly

A dog dressed as Santa Claus takes part in the annual city race in Skopje, Macedonia December 24, 2017.REUTERS/Ognen Teofilovski TPX IMAGES OF THE DAY

History enthusiast, dressed as a soldier, rides his horse during the re-enactment of Napoleon's famous battle of Austerlitz near the southern Moravian town of Slavkov u Brna, Czech Republic December 2, 2017. REUTERS/David W Cerny TPX IMAGES OF THE DAY

Activists attend a parade to demand rights of gender equality to LGBT community members in Santiago, Chile, November 25, 2017. REUTERS/Ivan Alvarado TPX IMAGES OF THE DAY

A Palestinian protester tries to push a donkey away from the the scene of clashes with Israeli troops following a protest against the near-by Jewish settlement of Qadomem, in the West Bank village of Kofr Qadom near Nablus August 25, 2017. REUTERS/Mohamad Torokman TPX IMAGES OF THE DAY

A participant reacts in front of a mock-up tank on fire as university students and relatives of victims march to commemorate the killing of students during a protest in 1975 by Salvadoran military forces, in San Salvador, El Salvador, July 30, 2017. REUTERS/Jose Cabezas TPX IMAGES OF THE DAY

Demonstrators stand near burning trucks while rallying against President Nicolas Maduro in Caracas, Venezuela, May 27, 2017. REUTERS/Carlos Barria TPX IMAGES OF THE DAY

A man breathes through an oxygen mask, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib, Syria April 4, 2017. REUTERS/Ammar Abdullah

A man breathes through an oxygen mask as another one receives treatments, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib, Syria April 4, 2017. REUTERS/Ammar Abdullah

A civil defence member breathes through an oxygen mask, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib, Syria April 4, 2017. REUTERS/Ammar Abdullah TPX IMAGES OF THE DAY

A masked reveller takes part in a spontaneous carnival characterised by improvisation, satire and the macabre, in the village of Ghaxaq, Malta, February 27, 2017. REUTERS/Darrin Zammit Lupi

A reveller wears a mask during carnival celebrations in Gijon, northern Spain, February 27, 2017. REUTERS/Eloy Alonso

A reveller wears a mask during carnival celebrations in Gijon, northern Spain, February 27, 2017. REUTERS/Eloy Alonso

Revellers participate in a flour fight during the "O Entroido" festival in Laza village, Spain February 27, 2017. REUTERS/Miguel Vidal

Masked reveller poses during the Venice Carnival in Venice, Italy February 20, 2017. REUTERS/Fabrizio Bensch

Revellers, dressed as "Zarramaches", walk through the streets during celebrations to mark Saint Blaise's festivity in Casavieja, Spain February 3, 2017. REUTERS/Sergio Perez

A woman breathes through an oxygen mask at al-Quds hospital, after a hospital and a civil defence group said a gas, what they believed to be chlorine, was dropped alongside barrel bombs on a neighbourhood of the Syrian city of Aleppo, Syria, early August 11, 2016. REUTERS/Abdalrhman Ismail