The Infected are inspired by George A. Romero's Zombies but also have original traits in Mad World they have limited intelligence being able to use heavy items to break through doors or glass and some use weapons to weaken an Survivor unlike George A. Romero's Zombies, The Infected are capable of running at a jogger's pace but depending on how damaged they are, some are either forced to walk or crawl. The Infected are also capable of walking up stairs and climbing up ladders once more, depending on what condition their body is in
The Infection is spread through Saliva so when an Infected bites someone the Saliva will touch the wound those who have recently became Infected can also spread it through kissing or other forms of contact.
The Infected are also known as The Dead but there is no reference to them actually being dead as the true cause of their reanimation is unknown while the popular speculation is a Virus and if this is true this implys that The Infected are not actually Dead in a traditional sense. The Infected soon decay over a peroid of time, the true cause of this is unknown.
The brain of The Infected is still active so they can still be classified as alive but have no control over their physical body and often share memories of their previous life.