Their findings say that 100 days after the zombie outbreak, a population 7.5 billion would be whittled down to "100 to 200 survivors." Those lonely, lonely people would be surrounded by 190 million zombies.
190 million zombies.
The point of their model is to predict how this hypothetical virus would spread. The zombies in the study are given a 20-day lifespan and have a 90 percent success rate of infecting at least one person every day. The epidemic also begins with only one person infected on "Day 0."
The study also put together another scenario that boosted the zombie lifespan to a year but added complications like human sexual reproduction and a 10 percent chance that people kill off one zombie each day. The human population still plummets, but recovery was able to eventually take root ...ahem... in about 27 years.