Idea
An idea is a virus for the mind.
Sometimes, an idea infects a large group of people, jumping from one person to the next, becoming ever more resistant. And just like an actual virus, an idea virus can cause delusions. The Little Prince was rightfully afraid that little seeds may grow into big trees and destroy his planet.
"A baobab is something you will never be able to get rid of if you attend to it too late." - The Little Prince