Spanish Flu
From January 1918 to December 1920, the world was hit with a particularly deadly influenza pandemic, also known as the Spanish Flu. About 500 million people, about a quarter of the world’s population at the time, died due to the outbreak.
Many think that the pandemic was especially deadly in Spain due to its name, but the truth lies elsewhere. During the outbreak, reports of the illness were minimized in the US, Germany, France and United Kingdom, likely in order to preserve World War I morale.
On the other hand, reports about the spread throughout Spain (who was neutral at the time) were not held back, even when it came to the infection of King Alfonso XIII.
Early on, it was believed that this influenza strain severely affected the immune system. But later findings claimed that the high mortality rate was due to poor hygiene, malnourishment and overcrowded medical facilities instead.