Knox Infection — How It Actually Works
Bites are 100%. Scratches are 7%. Lacerations are 25%. The roll happens the instant the wound lands, clothing only helps before that moment, and nothing in the vanilla game undoes it. Here is the whole system, without the folklore.
The single most useful habit: read the wound name on the health panel before you panic. Most deaths attributed to "a scratch" were actually bites that went unnoticed mid-fight.
The three wounds
Only zombie-inflicted wounds can carry Knox. The game picks the wound type first, then rolls once against the Knox chance:
| Wound | Knox chance (default) | How to read it |
|---|---|---|
| Bite | 100% | A death sentence under default Transmission settings. Plan the succession, not the cure |
| Laceration | 25% | One in four. Deep, bleeds hard, and can pick up an ordinary infection on top |
| Scratch | 7% | Usually survivable. Clean it, bandage it, watch for queasy over the next day |
| Non-zombie cut (glass, trees, falls) | 0% | Never Knox. Clean and bandage like any wound |
Three rules people miss: where the wound lands makes no difference — a scratch on the foot rolls the same 7% as one on the chest; each new wound gets its own roll — three scratches in one fight is roughly a 20% chance that at least one carried the virus; being attacked from behind or surrounded makes bites more likely, because drag-downs and pins favour the worst wound types.
One roll, at the moment of the wound
The Knox check happens when the wound is applied. Nothing after that moment changes the outcome: not disinfectant, not reloading the health panel, not waiting. What does matter is everything before:
- Clothing works before the wound, not after. When a zombie hits a covered body part, the fabric's bite or scratch protection can stop the wound entirely — tearing the garment instead of your skin. Bites check bite protection; scratches and lacerations check scratch protection.
- Thick Skinned / Thin Skinned change how often a hit tears the skin at all, which is how they shift your odds over a run.
- Once the wound is on your skin, clothing does nothing. Bandaging is for blood loss, not for Knox.
The 48–72 hour timer
On default settings (Infection Mortality: 2–3 days), the game picks a random death timer between 48 and 72 in-game hours. The clock runs in game hours, not real hours — with the standard day length that is roughly 3–4.5 real hours of play.
| Setup | Death window | Multiplier |
|---|---|---|
| No relevant trait | 48–72 hours (2–3 days) | ×1.0 |
| Resilient | 60–90 hours | ×1.25 — more time to stash and settle affairs, still fatal |
| Prone to Illness | 36–54 hours | ×0.75 — plan the end-of-life checklist earlier |
There is no fixed symptom ladder — older guides that promise "queasy at hour 6, fever at hour 40" are wrong. What actually happens: with no other source of sickness, the sick moodle tracks your progress through the timer. A rough reading:
- Queasy — around a quarter of the timer gone
- Nauseous — around half
- Sick — around three quarters
- Fever — near the end; health declines toward zero
"Infected" is not Knox
The single most common misread in the game. The health panel flag Infected on a body part means an ordinary bacterial wound infection — pus, a dirty bandage, a wound you forgot about. It is treated with cleaning, disinfectant and fresh bandages, and clearing it does nothing to a Knox timer.
| Signal | Ordinary wound infection | Knox |
|---|---|---|
| Health panel flag | "Infected" on the wound | None — the game never announces Knox |
| Caused by | Dirty wound, dirty dressing | Zombie bite / scratch / laceration roll |
| Curable | Yes — clean, disinfect, rebandage | No |
| Antibiotics help | Yes | No |
Other things make the sick moodle climb without Knox: rotten or undercooked food, uncleaned water, corpse sickness from living near bodies, and plain colds. Before you write off a character, check whether the sickness has a boring explanation.
What does not work
- Disinfecting the wound. Treats the bacterial infection. Does nothing to Knox.
- Antibiotics. Infection-reduction for ordinary wounds. Knox does not care.
- Bandages and sterilized dressings. Stop bleeding. Knox is not bleeding.
- Waiting to "see if it was just a scratch". The roll already happened. Waiting only burns the window.
- Any vanilla cure. There is none. Mods exist (the antibodies mod is the well-known one), but that is a different game, not this page.
When you know: the succession plan
Under default rules a confirmed bite is terminal, so the useful question changes from "how do I survive" to "what does my next character inherit". The world persists after death — use the window:
- Stash everything the next character needs: weapons, tools, keys, the generator, skill books — somewhere reachable and marked.
- Park a fuelled vehicle with a clear exit path near the stash.
- Spend noise deliberately. Some survivors clear their neighbourhood or lure hordes away on the way out — hours of work donated to the next run.
- The zombie-closet trick (community practice, not a game mechanic): strip your character, lock yourself in a small room, and die there. The reanimated zombie is contained, easy to find and safe to deal with on the next life.
What Build 42 changed
Nothing. This is worth stating plainly, because it is a recurring rumour: bite is still 100%, scratch still ~7%, laceration still ~25%, and the default death window is still 2–3 days. Every guide claiming B42 "softened" infection is describing a mod or a custom sandbox, not the game. The things that did change — armour crafting from hides, better protective gear via tailoring, basements for safer stash rooms — all work on the prevention side, which is the only side you control.
FAQ
What are the exact infection chances for bites, scratches and lacerations?
On default settings: bite 100%, laceration 25%, scratch 7%. Non-zombie wounds are 0%. The roll happens once, when the wound is applied, and nothing after that changes it.
Can you survive a bite in Project Zomboid?
Not in vanilla. With default Transmission settings a bite is always fatal. The only levers are sandbox settings (Transmission: None) or mods. What you can do is plan the succession: stash gear, park a vehicle, and make the next character's start easier.
How long does it take to die from Knox infection?
Default Infection Mortality is 2–3 days — a random window of 48–72 in-game hours. Resilient multiplies it by 1.25, Prone to Illness by 0.75. After death, the corpse reanimates in 0–1 minutes on Apocalypse defaults.
My health panel says "Infected" — am I going to turn?
Not from that flag. "Infected" on a wound is an ordinary bacterial infection: clean it, disinfect it, rebandage, take antibiotics if needed. Knox never announces itself on the health panel — the only signal is escalating sickness after a zombie wound with no other explanation.
Does washing a wound or taking antibiotics prevent Knox infection?
No. Disinfectant, sterilized bandages and antibiotics treat the wound and ordinary infections. Knox is viral and rolls at the moment of the wound — medical care after that point is irrelevant to it.
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Sources & verification
Infection odds (bite 100%, laceration 25%, scratch 7%), the 48–72 hour default mortality window, trait multipliers (Resilient ×1.25, Prone to Illness ×0.75), the 0–1 minute reanimation window and the unchanged-in-B42 status are cross-checked against multiple community references for 42.19–42.21 in November 2026. Transmission defaults are Blood + Saliva. Moodles are relative indicators, not a fixed hour-by-hour ladder — beware older guides that publish one. All values apply to default sandbox; changing Transmission or Infection Mortality in the sandbox menu changes everything on this page.