It's all over the games and I was wondeing if they ever mentioned it in the Anime. If they do, can you tell me what episode please?
Yes.
In Oaknapped, Professor Namba explained to Professor Oak that the mysterious viral lifeform Pokérus is an important component of the Pokémon Power Acceleration Project (PPAP), a secret project that aims to infect Pokémon with Pokérus to evolve them at a faster rate. However, all of his specimens have died out. Professor Oak also explains that the term "Pokérus" was coined by combining the words "Pokémon" and "virus" together. Later, Professor Oak began researching about the Pokérus.
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