Why is this movie called The Host?

What's great about the title is it gives everyone a chance to promote their ideas why it was called it.
Only the writer of the script knows for sure why it was call The Host.
All the replies in this thread are guess work and conjecture.
Nothing wrong with that cause it can lead to some great convos. Others are just plain silly.

I figured it was the river and sewers where he lived and fed.

I'm gonna have to watch it again but it seems I remember doctors saying there is and never was a virus? If so that being the reason for the title is blown out of the water.

Anyone can come up with something that sounds viable but in the end none of us really. Well unless someone here knows the writer and has a link to him telling the meaning. :D

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The movie is called the host because the monster in Hosting the girl in his sewer home. Simple as that. Has nothing to do with any virus.