YA fiction. Main character receives a message from future with code to prevent virus sent by Earth to eradicate humanity. Before 2013. Spoilers.

[Giovanna]

Spoilers!!! Definitely pre-2013, I remember this book was about a kid receiving a message/code from their future self with the info to prevent the events following in the book (we don’t know what the message is or where it came from until the end). The earth creates a macro virus (Y and X creatures) to eradicate humanity because we are destroying the earth. There’s one specific scene I remember of our protagonist wearing some protective suit and hiding in a pool from one of the viruses as the gas or whatever they emit cannot infiltrate water.

[Giovanna]

Let me clarify. The beings the earth sends are the earths version of immune cells created to destroy and fight the disease on earth (humans)

[Rainbowheart]

Do you remember any basics about the main character?

Male or female? Age?