Many years ago when I was in the Air Force I was billeted in the middle of a farmer's field in East Yorkshire. It was Xmas and I had just met a girl so I wasn't going home for the holiday. I let the other guys go and was looking after the place myself. The day after they had all gone I felt terrible. All our communications were switched off so I couldn't contact anyone. I just lay there for two days before I got up and was able to make a pot of tea.
I struggled through and after three days the girl managed to find me and went to the nearest village and got a doctor to call. I was feeling somewhat better but he examined me and got me some medicine. He told me that I had a particular virulent version that was called Asian Flu.
After that I got quite a lot of bad colds (not flu) over the years.
About twenty years ago we both had our first Flu jabs, ......and since then I have hardly had a cold.