The Influenza pandemic of 1918 (commonly known as the Spanish flu) lasted for nearly three years, from March 1918 to December 1920. About 500 million people were infected across the world, which had at the time a population of 1.80 billion people. The pandemic spread to remote Pacific Islands and the Arctic. It killed 50 million to 100 million people. This was three to five percent of the world's population at the time. It was one of the greatest natural disasters in human history.