Forgot to add that the Grippe Toxin in H1N1 is derived directly from the Spanish flu viral toxin. It is a small section of this toxin, this is why THEY needed to dig up those bodies.
What makes this so effective is that the toxin binds to the crystals of the Serialis Layered Head and alters the frq required to kill it.
This is why some are showing up with requiring extra Gelsemium runs to clear that and make these heads killable:
A word on these Grippe toxins; they are miasmatic and passed on down the generations. One person here addeed 17 new versions all by herself to the Doctrine.