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The Spanish Flu Epidemic

If you"re worried about the possibility of a coming bird flu epidemic, you can take comfort in the fact that humanity has survived a similar influenza epidemic in the past. Starting its rounds at the end of World War I, the 1918 flu killed an estimated 50 million people.
Popularly known as the Spanish Flu, this type of influenza was far worse than your common cold. Normally, influenza only kills those who are more vulnerable to disease, such as newborns, the old or the sick. However, the Spanish Flu was prone to killing the young and healthy. Often it would disable its victims in hours; within a day, they would be dead, typically from extreme cases of pneumonia(肺炎).
The Spanish Flu was quite nasty-fast-spreading and deadly. It managed to spread across the globe, devastating the world. Then suddenly, after two years ravaging(蹂躏)the Earth, it disappeared as quickly as it bad arisen.
Despite its nickname, the Spanish Flu did not originate in Spain. Its true origins are unknown. Some believe it started in US forts and then spread to Europe as America joined the war; others think that it populated the trenches of the English and the French and eventually broke out in 1918. Regardless of where it started, eventually a fifth of the world population suffered the disease, with a global mortality rate(死亡率) estimated at 2.5% of the population.
Modernity was partly to blame for the quick spread of the disease. It passed throughout the world on trade routes and shipping lines. It hit Northern America, Europe, Asia, Africa and the South Pacific. The war did not help at all—the movement of supplies and troops aided the spread of the Spanish Flu, as well as the trench warfare. Imagine the speed at which a virus can spread in a crowded ditch. The fast emergence of the virus in the trenches caused some soldiers to believe that the Spanish Flu was a new form of biological warfare.
Luckily, the Spanish Flu simply vanished by 1920. It is believed the flu simply ran out of fuel to spread.