Year of the Dead by Jack J. Lee
An advanced alien civilization sends out probes to study and preserve different planetary cultures and biospheres. A probe evaluates Earth and determines that humanity is headed toward extinction due to self-inflicted environmental degradation. In order to make Earth sustainable and to save humanity, the probe decides that Earth's population must be radically reduced.
The probe is programmed with prime directives that force it to make all interventions culturally appropriate. Since pop culture is full of movies describing the end of the world by zombies and vampires, the probe manufactures viruses that create an outbreak of these creatures. Ninety-eight percent of humanity is wiped out by culturally-sensitive environmentalist aliens who are here to save us.
This is a story of people living in Salt Lake City, Utah when the alien probe destroys the world. The unlucky, slow, and foolish die quickly. This isn't a typical zombie apocalypse story about a bunch of victims wandering the world slowly getting picked off one-by-one. This novel is about people, who refuse to be victims. They understand that the only way to survive is to band together and to control their environment. The aliens, zombies, and vampires need to be taught that on Earth the top predator will always be human.