These are some great questions. I did not know that the equator had a flu season
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haha! it doesn't!! yet it still gets the flu randomly. so it begs the question what is causing it there if these qualities of "seasonal transmission" are absent all year long.
we attribute the flu to the seasonal events that make transmission more likely yet we see the flu like symptoms in places where there are not augmented transmission qualities.
perhaps as you suggest it is from something not related to seasonality and more to do with human deficiency