What do you call the belief that the natural world is filled with spirits?

they are ..

Explanation:

both extremely small and need hosts to live. But a bacteria can survive a little while without a host. And while a virus is significantly smaller. They can both take over the human body with efficient ease. by reproducing and just growing more. so that they can take over the body alot faster than what the previous virus or bacteria did so they take more of the body instead of the little amount they previously did. Hope this helped.