OK, that's perhaps a bit of an exaggeration, but let's look at the Hugo list for this year, at least as far as I've got through it.
Of the 5 novels, two use the Z word
That's Deadline by Mira Grant, and Leviathan Wakes by James S. A. Corey
A third novel, A Dance With Dragons by George R. R. Martin, doesn't use the term. But it's the 5th novel in a series in which — well how shall I describe it? — dead people rise again and attack their former families and friends. Zombies by another name, and even if they don't feature during this novel, their existence is the great threat behind the series as a whole.
In the graphic story section, there is Schlock Mercenary: Force Multiplication by Howard Tayler. His current story (i.e. a year later in the online Schlock Mercenary publication) is also using the zombie trope, though we will have to wait a few more days to discover whether corpses infect.
(In the novella list Mira Grant reappears with Countdown, but I will just note that that's a prequel to her novel and not list it as another example. Also reappearing is Game of Thrones the TV series, which is the dramatic version of the 1st novel of which Dance with Dragons is the latest.)
So we have a whole swathe of stories from a bunch of writers in which zombies feature.
Is it a coincidence, or is there something in the concept of the zombie that allows writers to play with existential threat? Now that imminent nuclear destruction has gone, is our biggest threat the suicide bomber? Is the zombie a metaphor for the enemy that you cannot reason with, and that doesn't mind if he dies so long as you do too?
If so, how come Martin was there back in 1996, when Game of Thrones was first published?
(I'll also note autopope's Bit Rot, where it's a robot zombie outbreak.)