Viruses are things that latch onto other things without their permission. If you choose to build off of GPL code then yes, you must preserve the GPL license. There's an important difference.
It's actually the same as any other copyrighted code (and in the US, all code is automatically copyrighted and restricted). You cannot just take code and use it in your project. GPL code is nothing special.
It is very easy to accidently use a GPL library without knowing it, especially if it is a dependency of a dependency and you aren't using a license scanner.
It’s very easy to do all sorts of incorrect stuff if you totally ignore your responsibilities.
If you're not redistributing the GPL library, then it doesn't matter. If you are, then there are all sorts of other licenses which come with the same (or greater) headaches.
