Animism, Disease, and Elf-Shot

In Anglo-Saxon England, some diseases and many sudden pains were blamed on elf-shot, that is tiny or invisible arrows shot by elves into humans.  By the later middle ages, elves and fairies had become synonymous, and stone age arrowheads seen as evidence of their mischief; but this was not the case in the Anglo-Saxon era.

For a while I've had a hard time wrapping my head around this.  I'm a scientific person, married to an atheist with zero belief in the supernatural, and when hit with an ailment my first instinct is to take an aspirin and get some sleep.  It just wasn't in my worldview to believe there could be something more behind a lot of the sicknesses that science has pretty clearly identified.

But a thread on a forum I frequent has recently given me a new perspective on this issue.  It began with a poster asking about how animists treat bugs and other pests; can you kill something with a clear conscience if you believe it has a spirit?  For me, it was an easy answer - I don't generally bother things that don't bother me, but I don't feel badly about getting rid of bugs that are negatively affecting the life of me or my family in our own home.  But another poster in the thread brought up a good point about bacteria and even viruses - do animists believe that these have a spirit?

Que the "Aha!" moment for me!  As an animist, I do believe that bacteria and viruses have a spirit - but as beings that live on the sickness of humans or other animals, they are certainly negative spirits in our eyes.  And I believe now that this is where the entire notion of evil spirits comes from - early healers, trained both medically and spiritually, sensed the presence of these spirits who intended harm to human life, and developed both medicines and spiritual techniques to fight them.  This makes sense to me on a scientific and a spiritual level; and honestly, these are the kind of moments I live for - when something finally just makes sense.