eli5: Why was the second wave of the Spanish Flu so much deadlier than the first?

Question

eli5: Why was the second wave of the Spanish Flu so much deadlier than the first?

In: Biology

Answer 1

That is not widely accepted a true. A second wave in the US is believed to have killed more people because of wartime movements and other circumstances such as coinciding with season flu and pneumonia, some speculate the virus causing the Spanish Flu mutated and this is partly to blame – In short, no one knows exactly why.