Imagine if a new 'zombieism' disease broke out that spread through the commonly portrayed method of infected saliva that enters a person's bloodstream after being bitten by a zombie.

This kind of direct contact spread would normally be quite an inefficient method for disease transmission compared to airborne infections, which can be spread much more easily.

But zombieism is interesting because, like rabies, its symptoms can include anxiety, agitation, paranoia and terror that alter the behaviour of the infected individual.

So zombies will actively try to bite or eat their victims, thereby spreading the disease faster.

The original source of the zombie outbreak is rarely a concern in horror films, whereas epidemiologists spend a lot of time using analysis and models to track back to the first case of disease.