system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is blood poisoning?

I've just read the first *Hunger Games* book and it devotes a sizable part of the climax to Peeta's situation after he was stabbed by Cato. What exactly is blood poisoning and how does it kill?

Edit: A moderator automatically sent me a message saying I should Google this first. I have, but I'm still confused by all of the medical terminology. 

Second Edit: Holy shit, I didn't expect this to blow up, I just returned to Reddit after like 5 hours. Thanks for all of the responses, people!
gpt
Blood poisoning is what happens when an infection makes it into your bloodstream, which is your body's central highway for distributing and collecting stuff.

When you have a cold, you have an infection in your respiratory system. It's restricted to that area. When you have an ear infection, same thing. Or a skin infection. These colonies of bacteria are stuck in that spot; that is where they broke in and, hopefully, that's where they die when your immune system takes care of it. Blood poisoning (or sepsis) is when the infection isn't taken care of, and it breaks through and spreads *everywhere*, all at once. All of your organ systems become at risk, your immune system has to be mobilized everywhere (which means inflammation everywhere, causing another huge list of problems), your temperature spikes, and your body burns through resources like crazy. It's extremely dangerous, and highly fatal if not immediately treated.