Zombie Tunnels

Behold the newest super drug! The only side-effect is delusions, and three months after taking it your mind starts slowly disintegrating leaving you in a zombie state of mind. Literally.
Vivian Cross' mother, father, brother and sister are all missing. And when distraught soldiers come banging on her door seeking assistance, she's left with no choice. She must lead them through the treacherous, labyrinth of tunnels before the zombies become too organized whatever that means.
But along the way she faces her own demons i.e. her brother- the one that's alive, her apocalypse buddy, and bugs. Lots and lots of bugs.
Life's getting a whole lot more complicated, and until now she thought she had seen it all.