Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

Wu Lingling, a nurse from Central Hospital of Shanghai Fengxian District says goodbye to her husband Zhao Kun before leaving for Wuhan at Shanghai South Railway Station in east China's Shanghai, January 27, 2020. A team comprised of 50 medical workers from 40 hospitals in Shanghai left for Wuhan City on Monday to aid the novel coronavirus control efforts there. (Photo by Ding Ting/Xinhua News AgencyAlamy Live News)

Medical staff celebrate after all patients were discharged at a temporary hospital set up to treat people with the COVID-19 coronavirus in Wuhan in China's central Hubei province on March 9, 2020. China closed most of its makeshift hospitals for coronavirus patients, some schools reopened and Disney resort staff went back to work on March 9 as normality slowly returns to the country after weeks battling the epidemic. (Photo by AFP Photo/China Stringer Network)

A masked tourist poses for a souvenir photo next to a graffiti titled “Mobile World Virus” depicting “La Gioconda”, aka Mona Lisa, with a mobile phone and a medical mask, by urban artist TVBoy, close to the Sant Jaume square in Barcelona, Spain, 09 March 2020. Barcelona's Deputy Mayor and two town councillors are in quarantine after they were in contact with a City Hall's worker who was tested positive for the COVID-19 coronavirus. (Photo by Quique Garcia/EPA/EFE)

A prisoner from the Pedrinhas prison is carried to receive medical help after he was injured during a fight between rival gangs inside the jail, in Sao Luiz, capital of Maranhao state, January 8, 2014. The recent posting on a major Brazilian news website of a video filmed last December 17 by Pedrinhas prisoners of the decapitated and tortured bodies of rival inmates inside the jail has highlighted some of the problems present in the country's prison system which houses nearly twice as many prisoners as its capacity, according to official statistics. (Photo by Douglas Cunha/Reuters/O Estado do Maranhão)

A woman crowd-surfs in front of the main stage at the Woodstock Festival in Kostrzyn-upon-Odra, close to the Polish-German border, August 2, 2014. Some 500 thousand people attended the festival that is the brainchild of Polish journalist and social campaigner Jerzy Owsiak. He initiated the event to say thank you to those who donated money to his GOCC charity organisation that delivers medical care for children. (Photo by Thomas Peter/Reuters)