Hidden Symptoms Guide
Learn to detect symptoms that aren't visible during normal inspection - lab unlocks and UV detection.
What Are Hidden Symptoms?
Hidden symptoms fall into two categories: symptoms you haven't unlocked yet (must be discovered in the laboratory), and symptoms that are physically invisible without UV light.
Laboratory Symptom Unlocking
When you encounter a symptom you don't recognize, send the survivor to the laboratory to unlock it for future inspections.
UV Light Detection
The UV Tower reveals symptoms that are completely invisible during normal inspection. These are some of the most dangerous symptoms!
How The Lab Minigame Works
Send to Lab
If you see an unrecognized symptom, send the survivor to the laboratory instead of quarantine or living block.
Access the Computer
Follow them to the lab and wait for them to strap into the machine. Access the nearby computer to start the extraction minigame.
Control the Laser
Use W/S to raise/lower your aiming circle. A/D rotates around the survivor. Mouse controls a pointer bound to the aiming circle.
Color Codes
Orange = can destroy with left-click. Red = do NOT destroy (fails minigame). Green = extract target (hold E).
Extract the Sample
Destroy obstacles (orange) to get line-of-sight to the green target. Hold E to extract. Survivor dies but if not infected, no penalty.
Analyze the Sample
Pick up the extracted item from the box. Put it in the machine nearby and press E to create a vial. Put vial in analyzer to unlock the symptom.
Lab Controls
Orange
Destroy with Left-Click
Red
DO NOT Destroy!
Green
Extract Target (Hold E)
Laboratory Tips
- • You can only extract one item per survivor - choose wisely!
- • Extract a brain and carry it to the basketball hoop in the living block for an achievement.
- • Hitting too many red (forbidden) items will fail the entire minigame.
- • The survivor will die from extraction, but non-infected survivors don't count against your metrics.
Symptoms Requiring Lab Unlock
Green (Safe) - Lab Unlock
| Category | Symptom | Description |
|---|---|---|
| Skin Markings | Herpes | Small misshapen splotches, typically brown/red, without zits. |
| X-Ray | Fatty Hepatosis | Organ covered in yellow splotches. Note: Pancreas is always yellow - ignore it. |
Orange (Quarantine) - Lab Unlock
| Category | Symptom | Description |
|---|---|---|
| Skin Markings | Skin Rash | Rash full of zits and whiteheads with small splotches around. |
| Face | Mouth Bleeding | Blood coating lower lip running down toward chin. Be wary of beards hiding this. |
| Stethoscope | Nonspecific Respiration | Heavy wheeze and some gurgling mixed in. Listen carefully at black spots on lungs. |
| X-Ray | Color Differences | Organ colored normal purple or slightly pinkish purple instead of healthy red. |
Red (Liquidate) - Lab Unlock
| Category | Symptom | Description |
|---|---|---|
| Face | Eye Pus | Small drop of green pus on corner of one eye. Can be very small and hard to see. |
| Face | Nose Pus | Drop of green pus from one nostril, usually prominent. Watch for mustaches. |
| Stethoscope | Zombie Growl | Sounds like a zombie growling instead of any kind of breathing. Unmistakable sound. |
| X-Ray | Moldy Organ | Organ colored teal blue. Check liver (base layer) and brain (third layer). |
| X-Ray | Organ Necrosis | Organ almost fully covered in dark black splotches. May require unlocking twice due to bug. |
UV Light Detection
How to Use UV Tower
Press the button on your inspection table to bathe the area in UV light. It lasts a few seconds and needs time to recharge, but can be used multiple times.
Critical Warning
UV-Only Visible Symptoms
| Symptom | Danger | Description |
|---|---|---|
| UV Vapor | Safe | Green mist surrounding some part of survivor. Fly buzzing sound may indicate this symptom. |
| UV Contraband | Liquidate | Green glowing spot on backpack items. Check BEFORE confiscating! Survivor with contaminated items = infected. |
| Hidden Bite Mark | Liquidate | Zombie bite invisible normally, glows green under UV. Anywhere on body including under clothes. |
| Hidden Necrosis | Liquidate | Black splotches invisible normally, glow green under UV. Don't confuse with visible tattoos! |
| Hidden Eye/Mouth Pus | Liquidate | Green pus invisible normally, glows brightly under UV. Check corners of eyes and nostrils. |
Using the Symptom Scanner
At later base upgrades, the entrance metal detector can be upgraded to detect symptom categories. Each lit symbol indicates the survivor MIGHT have symptoms from that category (false positives possible). If a symbol doesn't light up, you can skip checking that category entirely.