Copying Google AI's response here as it's at least as good as what I was going to recall:

> Fever is a key part of the innate immune system, acting as a protective response to infection by raising the body's temperature. This increase in temperature inhibits the growth of many pathogens, enhances the activity of immune cells like leukocytes, and improves the effectiveness of the adaptive immune response.

My Vietnamese in-laws commonly make a sweat tent to shorten the duration of sickness. I can't say if it works, but it's something I intend to try next time I'm sick.

When I feel like I have a virus I usually put on my hoody which I only wear when I feel ill and a scarf and before going to bed I drink a lot of herb or ginger tea (like two cans)

this is will heat up your body and you get some night sweats, this usually helps reducing the sick time.

I can't say if it actually helps, but its become a ritual for that occasion