In 1918, toward the end of World War I, the Spanish flu swept the world, infecting an estimated 20 % of the world's population. Military units dispatched across continents and cramped together in unsanitary living conditions provided ideal conditions for the spread of influenza. A great many also perished in the cities, where electric trams were used to clear away the corpses.
一九一八年，「西班牙流行性感冒」侵襲全球，當時正值第一次世界大戰末期，估計全世界有五分之一的人口受到感染，尤其歐、美各洲間四處調動、擁擠而衛生條件不良的軍營，更成了流感病毒滋生蔓延的大本營；城市中的死亡也無所不在，為了加緊清運屍體，連電車都派上了用場。