Knox Infection

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“The Knox Infection's final stage is one of violence.”
— Kirsty Cormick
Knox Infection (commonly known as zombie infection) is a highly contagious disease contracted only by humans. This disease is very different from the common cold, food poisoning or wound infection. It is the main catalyst and antagonist for the events that unfold in Project Zomboid, dubbed the Knox Event.



Very little is known about the origin of the disease, other than that it began in the state of Kentucky, U.S.A, in rural area of Muldraugh and West Point. There are several rumours about the origin, such as: misfolded prions in the meat of Spiffo's, terrorist attack, bioweapons testing gone wrong, and God's punishment for the sins of Man.

Initial outbreak

The exact date of the initial outbreak is unknown and estimated to be between July 2 and July 6, 1993 (one week prior to the start of the game). The Knox Infection began to spread throughout the area of Muldraugh and Kentucky, KY. The military set up a blockade around the affected area before it managed to spread further, containing the outbreak. At first, the government portrayed the outbreak to be flu-like, causing panic and confusion among the infected. The infection is known to spread through fluid-contact: being scratches and bites.

Five days after the blockade went up, the WHO grounded all non-military or -medical international flights, which lead to mass panic throughout the nation and a disgruntled response from the President. The response and lack of clarity from the United States government lead to international leaders condemning America, with the UK premier criticising the President’s “near lack of clarity”. A photo from West Point is leaked out of the Exclusion Zone, with an image of a man covered in blood and bites, one arm missing, in a street crowded with dead.

Second wave

After 8 days, shots and explosions occur at the border of the exclusion zone, catching the attention of infected civilians, leading to hundreds, maybe thousands breaking through the blockade. Within two days, the infection spread North to Louisville, KY, littering the streets in dead along the way. As a last resort, the military blew the bridges across the Ohio River, leaving those left in Louisville to fend for themselves.

Something is released with the wave of the dead, as people begin showing symptoms of the infection without coming into contact with any infected. The Knox Infection quickly spreads throughout U.S.A, breaking down society, and even spreading across the ocean to Europe, Asia and Africa.


The infection is known to only infect humans through bodily-fluid contact – such as bites and scratches – and at some point ‘evolved’, infecting those even without fluid contact. It takes up to three days for the infection to eventually kill its host, upon being reanimated within an hour after death.


The pathophysiology of the infection is never mentioned during the events of Project Zomboid. However, it is likely of viral or prion origin, as it’s mentioned to be “flu-like” (virus) and Professor Peter Endsleigh draws a connection between Mad Cow disease (prion) and the fact that the infection is “clearly a neurological disorder”. There are no known cases of surviving the infection, and so therefore the body’s counteractions are unknown.


Certain people such as the player possess a natural immunity to the infection’s transmission method of non-fluid contact, however they will still contract the infection upon fluid contact.

Game mechanics


The game will never outright tell the player that they are infected and will instead become more stressed and sick over time. After just three hours, they will begin to feel anxious, as their fear of being infected worsens. If their stress condition is left untreated, after being infected for just 12 hours, they will begin to feel sad - affecting their rate of recovery from fatigue and exhaustion, as well as affecting their weapon accuracy. 14 hours later, symptoms from the infection will begin to show - displayed by the sick moodle. 18 hours in, the symptoms worsen as the body begins to degrade, losing health. The rate in which health is lost can be slowed by staying well rested, hydrated and well fed, however rate of health loss will only increase as time progresses. Eventually, the infection will become so bad that it is impossible to stop the infection from progressing towards death, even by being 'Full to Bursting', well rested and hydrated. It will usually take 2-3 days for the infection to kill the host. Up to an hour after killing the host, the body will reanimate, becoming a zombie and begin to wander the same as other zombies.

Infection rate

It is only possible to contract the Knox infection by getting scratched, lacerated, or bitten by a zombie. The probability depends on the type of injury. Non-zombie related injuries will never result in contracting the infection.

Transmission Probability
Scratch 7%
Laceration 25%
Bite 100%


The hypochondriac trait will cause the player to occasionally get the symptoms of the zombie infection after receiving a scratch, without actually being infected. The progression is identical to the Knox Infection, however once the 'fake infection' reaches its peak, the infection will dissipate as the player begins to recover. The rate of recovery is much quicker than the infection's progression.

Popular myths

  • "There is a small chance to survive a zombie bite" - this is referring to a previous bug that resulted in a ~96% chance of surviving a zombie bite, and has since been fixed, making a zombie bite 100% lethal.
  • "It is possible to recover from the infection with enough sleep, food and drink" - this may have been caused by the hypochondriac trait, general food sickness or even confusion with wound infection. It is impossible to survive the 'real' infection.
  • "Disinfecting the wound immediately and regularly will destroy the infection" - this is not the case - once infected, there is no way to remove the infection.
  • "Zombies with blood on their hands are more likely to infect with scratches" - while this makes physiological sense, this is not the case. Zombies with bloody hands have usually climbed through a broken window.
  • "It is possible get infected by climbing through a broken window without clearing the glass first" - the infection can only be contracted from a zombie in person. The infection does not exist outside the body.

Popular facts

  • "Dying before the infection kills you (drinking bleach), will stop your body from reanimating after death": this is true, and can be done to stop the body from wandering off with all their posessions, allowing the player to create a new character and return to their dead body.


  • Infection lore is heavily based off of George A. Romero zombies, with some very minor alterations.