While playing a virus infection in Plague Inc (Android), the Insomnia symptom has been randomly mutated, and it cannot be devolved. The Devolve button is visible, but greyed out.

It's the early stage of the game (just the second country has been infected), and the only one earlier mutated symptom (coughing) could be devolved (I think I got 1 DNA point for it returned).

How come this symptom cannot be devolved?

2 Answers 2


The more you devolve, the more it costs to devolve.

Depending on the disease type, the initial cost can be negative (thus you get DNA back for devolving). This is why you got DNA back at first, and why it now costs DNA to devolve.

There are 2 genetic codes related to devolution costs:

  • Ionised Helix
    This gene grants bonus DNA when devolving (+2 DNA Points for devolution). This gene is useful at lower difficulties because devolution of low-tier Symptoms, for example, frees up DNA Points that can be used to evolve higher-tier symptoms. In general, it reduces the total cost.

  • Translesion +
    Costs to devolve don't increase. This is useful with Virus and/or high difficulty modes, because of high amounts of symptoms and high costs of symptoms respectively.

The initial cost of devolving also depends on the disease type. For instance, the bacteria refunds 2 DNA (you receive 2 DNA points) when devolving for the first time, while the virus costs 3 DNA points (you pay 3 DNA points).

  • Thanks, this information is much more precise than what I found out so far. Commented Apr 23, 2020 at 14:56

I already found the answer.

It cost DNA points to have it devolved, and it seems I misread the first devolve, by it COSTING one DNA instead of returning it.

Since I did not have enough DNA points to devolve the second, the button was grayed out.

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