Uh

So what you're saying is

That instead of an infectious disease

The Pika Flu is actually some kind of random lightning bolt that comes from the sky and smites you into Pikachu-dom.

...Mate if she wants to be a Pikachu she'll be a Pikachu. though I do recall she'll be a flu-free Pikachu as having access to Neo's banners is PERMANENT PROTECTION FROM FLU. So you'll only be a Pikachu.