Pyrexia (or fever) is mostly considered just high temperature, most often caused by infections. Especially in this time of the year, influenza infections that cause fever are quite common.
I would presume that the body heats up in order to kill off bacteria (similar as to why we boil water, and cook food). This doesn't really make much sense when it comes to viruses, as they do not have a similar metabolism. Still, one symptom of influenza is pyrexia, so I conclude that pyrexia is triggered in some part of the immune system which does not differentiate between a viral and bacterial infection. I imagine pyrexia to be the body's standard response to an intruder of any kind. Am I right here?
I also do have 2 follow up questions: How does our body increase the temperature? Is there a fail-safe mechanism (the many deaths caused by high temperature make me think there is none)?
For those who listen to R&B: I'm not looking for the song by Peggy Lee (which is great, by the way)