Most victims were healthy young adults, in contrast to most influenza outbreaks, which predominantly affect juvenile, elderly, or weakened patients.
The pandemic lasted from June 1918 to December 1920, spreading even to the Arctic and remote Pacific islands. Between 50 and 100 million died, making it one of the deadliest natural disasters in human history. Even using the lower estimate of 50 million people, 3% of the world's population (1.86 billion at the time) died of the disease. Some 500 million, or 27% (≈1/4), were infected.
Pandemic flus are the exception, not the rule. None of us may see one in our lifetimes, even if we have (and recover from) a dozen cases of seasonal flus. Also, some believe the death rates from the 1918 pandemic were more due to concomitant bacterial infections than the flu strain itself.
