Project Zomboid Knox Infection Mechanics: B41 vs B42.19
Build 42.19 · Scratch, cut, and bite Knox odds · Transmission & Mortality timing
Mechanics at a glance
Default odds
- Scratch: 7% Knox chance
- Laceration / cut: 25%
- Bite: 100% (blocked only by Transmission = None)
When rules apply
Transmission and Mortality are evaluated as infection is applied. A later setting change is not a guaranteed way to rewrite an infection already on the character.
What treatment changes
Bandages, disinfectant, and antibiotics can manage the body-part wound or its ordinary infection. They do not clear a true Knox infection in vanilla.
Wound infection odds (default Blood and Saliva)
Knox chance is rolled when the wound is applied. The game does not print “you got the virus” on the Health panel. Under default rules: scratch ~7%, laceration / cut ~25%, and bite 100% unless Transmission is set to None.
| Wound | Default Knox chance | Notes |
|---|---|---|
| Scratch | ~7% | Still dangerous; many runs end on “just a scratch.” |
| Laceration / cut | ~25% | Same roll model as scratch with a higher chance. |
| Bite | 100% | Only Transmission = None prevents bite infection. Other Transmission modes still allow bites to set Knox infection. |
Three different infection states
True Knox infection
Stored separately from the Health panel's ordinary wound flag. Under a lethal Mortality option it progresses toward death and reanimation; vanilla medical items do not clear it.
Fake infection
A nonlethal sickness track that can fade. Under Build 42.19 Mortality = Never, a newly applied true infection is converted to this state when infection is applied.
Ordinary wound infection
The body-part Infected label is a treatable wound condition. It neither confirms nor rules out Knox, and treating it does not alter the hidden Knox state.
Sandbox: Transmission and Mortality (Build 42.19)
UI path: Custom Sandbox → Zombie Lore → Transmission and Mortality. For a step-by-step “turn infection off” checklist, use Turn Off Infection (Transmission = None).
Transmission options
| UI label | What it does in-game |
|---|---|
| Blood and Saliva | Default-style spread: scratch ~7%, laceration ~25%, bite 100%. |
| Saliva Only | Scratch / laceration Knox rolls are cleared. Bites still infect (unless you also use None). |
| Everyone’s Infected | Lore / reanimation framing differs from “you only catch it from a wound,” but wound rolls are not free immunity: bites still set infection; scratch / cut rolls are not auto-cleared the way they are under Saliva Only or None. |
| None | No new Knox infection from zombie attacks, including bites. This is the real “turn off transmission” switch. |
Mortality is part of the application path
Mortality selects the lethal time band for a newly applied true infection. Apocalypse uses 2–3 Days. Never takes a different path: when infection is applied, the true flag is converted to fake infection so it can fade without the lethal countdown.
Build 41 vs Build 42.19 boundary
| Question | Build 41 | Build 42.19 |
|---|---|---|
| Default wound odds | Scratch ~7%, laceration ~25%, bite 100% under Blood and Saliva. | Same default odds under Blood and Saliva. |
| Vanilla cure | No stock medical cure for true Knox infection. | Expanded crafting and medical content still does not add a stock Knox antidote. |
| Sandbox concepts | Transmission and Mortality still govern infection rules; keep branch-matched sandbox files for each build. | Same concepts under Zombie Lore: Transmission and Mortality control new infections and lethal timing. |
| Mods | Compatibility is branch-specific. A mod claiming B41 support is not evidence that its B42 package, dependencies, or save migration are safe. | |
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