COVID-19 and Flu Pandemics Follow a Pattern: A Possible Cross-immunity in the Pandemic Origin and Graver Disease in Farther Regions.

So far, the COVID-19 pandemic has caused less casualty in Eastern Asia areas compared to the other parts of the world. The pattern of less casualty in the pandemic origin has also been observed in the three main flu pandemics in the last century. It is reasonable to speculate that less casualty of COVID-19/flu in the pandemic origin is likely due to the preexisting cross-immunity to some close viruses being more prevalent in those regions. Experts and modelers should scale up the severity of a flu-like viral epidemic to predict its real severity for the rest of the world.