Variola (Smallpox)

Hi,

I am a student in High School and I am doing a report on the variola virus.
I've already found many sources in my local library and on the internet.
However, I am looking for a more detailed description of exactly how the
virus operates in the human body.

If anyone could provide a few links to some reputable sites or the titles of
some books, it would greatly assist me.

Thanks.