Once the virus developed the ability to be transmitted from person to person, the situation spun out of control as the disease spread throughout the world, killing between 20 and 50 million people in a matter of a few months.
當時病毒產生人傳人的能力後，一發不可收拾，從西班牙蔓延到全球，在短短幾個月內，造成全球 2000 萬到 5000 萬人死亡。