the 1918 pandemic(English: 1918 influenza pandemic), a global influenza epidemic that occurred between 1918 and 1919, was caused by an infectious disease known as the Spanish influenza, which once infected approximately 1 billion people worldwide and killed 25 million to 40 million people (the world population at that time was approximately 1.7 billion people); its global average fatality rate was about 2.5%-5%, which is more deadly compared to 0.1% of the general influenza. Its name is not because the influenza broke out in Spain; rather, it is called the Spanish influenza because about 8 million people in Spain were infected with the disease at that time, and even the King of Spain was infected with the disease. As for Spain, it is called the French influenza.

On October 31, 1918, public health officials in the United States and abroad estimated that the influenza that was spreading around the world would kill 20 million or more people.

The plague spread around the world with unprecedented speed and toxicity. New strains of influenza bacteria seem to first appear in Spain. It quickly spread among European and U.S. troops and seriously endangered people weakened by war-induced stress and malnutrition. The plague quickly spread from Europe to Asia, killing millions of people in China alone.

In the United States, the Federal Public Health Service revealed that civilian mortality rates far exceed those of troops abroad, and that more soldiers die of influenza than those who die in battle. In the past two months, reports from 46 cities, accounting for one-fifth of the country's population, put nearly 80,000 deaths from influenza. According to the Health Bureau, the epidemic has peaked so far in the two weeks leading up to October 26, with 40,000 deaths.

Attempts to develop an anti-influenza vaccine have not been successful, and medical sources in most countries are stretched to the extreme, leaving little hope of ending the epidemic.