Israeli soldiers play the parts of wounded civilians during a drill simulating a toxic spill from an attack on a train in Beersheba, southern Israel, 13 January 2016, as Home Front medical teams, fire fighters and police carry out rescue operations. The large scale drill is the concluding exercise of the Fourth International Conference on Healthcare System Preparedness and Response to Emergencies and Disasters and includes some 200 of the world's experts on health system readiness from around the world. The conference is dealing with all types of medical emergencies from terrorist attacks to natural disasters. (Photo by Jim Hollander/EPA)

An incredible clear-air lightning display from storms to the east of Noonamah, just outside Darwin on April 6, 2015. (Photo by Jacci Ingham/The Guardian)

A wild leopard runs on the stairs as it tries to escape from a compound of a house in Kathmandu, Nepal June 1, 2016. (Photo by Navesh Chitrakar/Reuters)

Detainees look out from a prison cell at a compound of the Lukyanivska detention centre in Kiev, Ukraine, July 19, 2016. (Photo by Valentyn Ogirenko/Reuters)

Labourers unload gravel from a boat docked in Dala township, opposite Yangon city, Myanmar, November 12, 2015. (Photo by Olivia Harris/Reuters)

A picturesque supercell formation in the northwest of Booker, Texas from June 2013. (Photo by Mike Olbinski/Barcroft Media)

A volunteer approaches a male toad to pick him up from a road near Berlin on March 18, 2012 in Gueterfelde, Germany. (Photo by Sean Gallup/Getty Images)

A man crosses Canal Street in the wind and rain from Hurricane Isaac August 29, 2012. (Photo by David J. Phillip/Associated Press)