I disagree with the model.
Humans in the removed class can resurrect and become a zombie (parameter ζ ).
Zombies move to the removed class upon being ‘defeated’. This can be done by removing the head or destroying the brain of the zombie (parameter α).
I'm disagreeing with the assumption that destroyed zombies would resurrect as new zombies. Surely, if it is destroyed by removing head (or enough other parts), then it couldn't resurrect?
The model should have two dead classes:
(R) dead and able to resurrect
(D) dead and unable to resurrect (properly destroyed zombies).
So this is the correct model:
S' = Π − β S Z − δS
Z' = β S Z + ζ R − αS Z
R' = δS − ζ R
D' = αS Z
Also, if people who die natural deaths are also properly destroyed to preemptively prevent their future zombification, then this is the correct model:
S' = Π − β S Z − δS
Z' = β S Z + ζ R − αS Z
R' = − ζ R
D' = αS Z + δS
So R=0
Hence,
S' = Π − β S Z − δS
Z' = β S Z − αS Z
D' = αS Z + δS
Then as long as α > β, the zombies are under control, and will eventually be eliminated.
The report is just scaremongering. Don't believe the lies.