Rows of infected people assembled into warehouses suffering from 1918 Influenza Pandemic. A total of 50-100 million people were killed, ca.1918.
The 1918 flu was unusual in that it heavily affected the young and the healthy. “Normal” influenza mostly kills the weak/elderly. This flu, however, induced what is known as a cytokine storm in those who were strong and healthy— basically your immune system would freak out and go into a positive feedback loop and drown you with fluid and white blood cells in the lungs.