The Spanish Flu pandemic of 1918-1919 spread rapidly around the world and resulted in an estimated 20-50 million deaths. The virus was highly contagious and spread easily through close contact between people. While many died, some see a small consolation in that exposure may have provided some immunity to future pandemics. The viruses that caused the Spanish Flu were particularly deadly due to multiple mutations, including some that occurred after being transmitted between different animal species like pigs, before infecting humans. With today's global air travel and population densities, a similar virus could potentially spread even faster and cause an even larger loss of life.