It will take just 100 days for zombies to take over the world and reduce human survivors to a population of less than 300, a new study says.
According to the study at University of Leicester in the UK, the students assumed that if a zombie can find one person daily, with a 90% chance of infecting victims with the zombie infection, then by day 100, there would be just 273 human survivors remaining, outnumbered a million to one by zombies.
The team, which presented the findings in the student-run Journal of Physics Special Topics, investigated the spread of a hypothetical zombie virus using the SIR model - an epidemiological model that describes the spread of a disease throughout a population.
The model splits the population into three categories - those susceptible to the infection, those that are infected and those that have either died or recovered.The SIR model then considers the rates at which infections spread and die off as individuals in the population come into contact with each other.
As part of the formula, the students looked at S (the susceptible population), Z (the zombie population) and D (the dead population), suggesting that the average life-cycle of a zombie would be S to Z to D.
They also examined the time frame over which individuals in the population encounter one another.
The initial study did not factor in natural birth and death rates, since the hypothetical epidemic took place over 100 days, resulting in natural births and deaths being negligible compared to the impact of the zombie virus over a short time frame.
Without the ability for humankind to fight back against the undead hordes, the students’ calculations suggest that if global populations were equally distributed in less than a year the human race might be wiped out.
However, in a more hopeful follow-up study, the students investigated the SIR model applied to a zombie epidemic and introduced new parameters, such as the rate in which zombies might be killed and people having children within the nightmare scenario. This made human survival more feasible.
The team factored in how over time survivors may also be less likely to become infected after having experience of avoiding or fending off zombies.
They found that it would be possible for the world’s human population to survive the zombie epidemic under these conditions and that eventually the zombie population would be wiped out and the human population would recover.
“Every year we ask students to write short papers for the Journal of Physics Special Topics. It lets the students show off their creative side and apply some of physics they know to the weird, the wonderful, or the everyday,” said Mervyn Roy, a lecturer at Leicester’s department of physics and astronomy, said.