Plague Inc.: How to Unlock the Brown Streets Achievement

To unlock the Brown Streets achievement in Plague Inc., mutate both Diarrhea and Insanity on the same pathogen. The achievement triggers immediately once both symptoms are active at the same time, producing an in-game news popup about public bowel control. You do not need to wipe out humanity or win the game to earn the unlock.

Recommended Setup

Using a standard Bacteria run on Casual difficulty provides the easiest environment to gather DNA and avoid cure pressure while branching across separate symptom trees.

• Pathogen Type: Bacteria. It has predictable symptom costs and no inherent cure acceleration mechanics.
• Difficulty: Casual or Normal. Casual keeps medical research slow and eliminates DNA cost penalties.
• Starting Country: India or Saudi Arabia. Both feature dense populations with land and sea connections to accelerate early infection bubbles.
• Gene Setup (Optional): If unlocked on your profile, equip ATP Boost for starting DNA, Sympto-Stasis to prevent symptom costs from scaling, and Genetic Mimic to slow cure research.

Evolution Sequence

Because Diarrhea and Insanity sit on opposite sides of the symptom grid, establish a light transmission base first to secure steady DNA generation from infections.

1. Build Basic Transmission

Evolve basic transmission vectors so the pathogen can cross borders and reach sea ports:

• Water 1
• Air 1
• Bird 1
• Cold Resistance 1 (Evolve this if the infection reaches colder regions like Canada or Greenland so transmission does not stall.)

2. Mutate the Digestive Tree

Work down the digestive symptom branch to unlock Diarrhea:

1. Nausea
2. Vomiting
3. Diarrhea

(Optional combo): Mutating Sneezing alongside Diarrhea triggers the secondary "Oops" combo, which provides bonus infectivity.

3. Mutate the Neurological Tree

Work down the neurological branch to unlock Insanity:

1. Insomnia
2. Paranoia
3. Seizures
4. Insanity

Managing Cure and Lethality Risks

Evolving Insanity causes a sharp spike in disease Severity. While Insanity slows laboratory research by confusing scientists, the sudden awareness jump prompts global cure funding.

• Reserve DNA for Cure Defense: Keep 15 to 25 DNA points banked before evolving Insanity. If cure progress approaches 50%, purchase Genetic Hardening 1 and 2 under the Abilities tab. Use Drug Resistance 1 or Genetic ReShuffle if you need to roll back cure percentages.
• Avoid Lethality: Do not evolve high-lethality symptoms like Total Organ Failure, Necrosis, or Hemorrhagic Shock. If hosts die faster than the infection spreads, your DNA generation will collapse before you can afford Insanity.
• Devolve Random Lethal Mutations: If your pathogen spontaneously mutates lethal symptoms, devolve them immediately to protect your infected host pool.