The second wave of the infamous Spanish flu was even more deadly than the first - and experts have warned the same could happen with the coronavirus pandemic.
It first emerged in March 1918 at an army base in Kansas and by the end of the month 38 soldiers had died and 1,100 people had been hospitalised.
The ongoing war meant soldiers were being shipped across the globe - helping the virus spread in the years before air travel.
It went on to kill anywhere between 50 million and 100 million people with three waves and infected around a third of the world’s population.