A subway train runs in Kiev, Ukraine, May 25, 2020. The subway in Kiev reopened on Monday. Passengers must wear masks and keep social distancing guidelines. Due to the COVID-19 pandemic, the subway in Kiev was out of service since March 17. (Photo by Sergey Starostenko/Xinhua)

Passengers wearing face masks take the subway in Kiev, Ukraine, May 25, 2020. The subway in Kiev reopened on Monday. Passengers must wear masks and keep social distancing guidelines. Due to the COVID-19 pandemic, the subway in Kiev was out of service since March 17. (Photo by Sergey Starostenko/Xinhua)