system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do Cystic Fibrosis patients have to stay 6 feet apart from other CF patients, but not anyone else?

I can’t find ANYTHING about this on the internet. What makes CF patients so dangerous to other CF patients that they have a distance requirement, but with people who aren’t sick, you can be as close as you’d like?
gpt
Cystic fibrosis, among many other things, causes very thick mucus to build up in the lungs. This creates an ideal environment for certain types of bacteria that aren't normally found in people's lungs, such as specific strains of *Pseudomonas aeruginosa*. CF patients staying away from one another is to stop these specific bacteria from passing between them.