ZN1 is the Center for Disease Control (CDC) designation for the undead-creating virus that is responsible for the global zombie apocalypse.
Very little is known - or at least widely known - about its origins.
Symptoms of ZN1 include, but are not limited to:
- Damaged nervous system with limited cognitive activity.
- Violent tendencies towards non-infected individuals.
- Acute sensing, visual and auditory range, of non-infected individuals or repetitive sounds.
- Physical activities are limited to standing under balance, crawling or shuffling/walking or running (for recent infected only), grabbing and attacking, and biting.
- Increased resistance to traumatic physical injury except to the head/brain.
- Head/brain trauma kills ZN1 victim.
ZN1 is transmitted through bite, leading to a rapid transition to a zombie, or after a non-zombie individual dies, leading most people to realize that everyone is infected.
The only known survivor of direct contact is an involuntary test subject from the Portsmouth Naval Prison's infection control laboratory.
Murphy was injected with an experimental vaccine, which - unlike previous versions tested on other inmates - did not turn him into a zombie. He was then bitten 8 times by infected and zombified individuals, again not contracting the virus.
It is believed that he holds the key to mankind's salvation in the form of antibodies his immune system formed as a result of his exposure to the vaccine. Operation Bite-mark was then established in order to deliver him to the CDC research facility at Mount Wilson Station in California - at all costs.