Plot Question 

As anyone found any refernces to how the plot or story line for this show is supposed to work?  How to they explain how 90% of humanity (apx 6.3 billion people) get wiped out in a couple of day within the whole of Earth's biosphere being wreaked?  It would be nice if someone could find stuff like that to add to the article to help make it better.  How do they explain all of the military being killed while all the cities and towns still standing?  That makes no sense.  So perhaps some help here would be great.