system
Given the following post, respond as if you're commenting on Reddit:
human
Are there any viruses that humans must have in/on our bodies in order to stay alive?
gpt
It’s possible that some bacteriophages (viruses that infect bacteria) are important for keeping gut bacteria in check, though it might be hard to prove that one way or another.

Alternatively, there are parts of the human genome that are theorized to have originally come from viral DNA, so if you count those as viruses still, they are very essential.