Nurses attend a concert by Fado music group Serenata ao Luar at Santa Maria Hospital in Lisbon, Portugal, May 12, 2020. A concert was held by Fado music group Serenata ao Luar on Tuesday to mark the International Nurses Day amid the COVID-19 pandemic. (Photo by Pedro Fiuza/Xinhua)

Photo taken on May 12, 2020 shows a concert by Fado music group Serenata ao Luar at Santa Maria Hospital in Lisbon, Portugal. A concert was held by Fado music group Serenata ao Luar on Tuesday to mark the International Nurses Day amid the COVID-19 pandemic. (Photo by Pedro Fiuza/Xinhua)

Nurses attend a concert by Fado music group Serenata ao Luar at Santa Maria Hospital in Lisbon, Portugal, May 12, 2020. A concert was held by Fado music group Serenata ao Luar on Tuesday to mark the International Nurses Day amid the COVID-19 pandemic. (Photo by Pedro Fiuza/Xinhua)

Nurses attend a concert by Fado music group Serenata ao Luar at Santa Maria Hospital in Lisbon, Portugal, May 12, 2020. A concert was held by Fado music group Serenata ao Luar on Tuesday to mark the International Nurses Day amid the COVID-19 pandemic. (Photo by Pedro Fiuza/Xinhua)

Members of Fado music group Serenata ao Luar participate in a concert for nurses at Santa Maria Hospital in Lisbon, Portugal, May 12, 2020. A concert was held by Fado music group Serenata ao Luar on Tuesday to mark the International Nurses Day amid the COVID-19 pandemic. (Photo by Pedro Fiuza/Xinhua)

Nurses attend a concert by Fado music group Serenata ao Luar at Santa Maria Hospital in Lisbon, Portugal, May 12, 2020. A concert was held by Fado music group Serenata ao Luar on Tuesday to mark the International Nurses Day amid the COVID-19 pandemic. (Photo by Pedro Fiuza/Xinhua)