What is the world wide epidemic killed 30 million people and lasted two years in World War 1?

The worldwide epidemic that killed approximately 30 million people during World War I is known as the Spanish flu. It spread rapidly between 1918 and 1919, affecting a significant portion of the global population. The virus was particularly deadly due to its ability to infect healthy young adults, leading to high mortality rates. The pandemic had profound social and economic impacts, compounding the devastation of the war.