Any rocky mountain spotted fever experts out there ?

The doctor thinks a friend might have this.
The question is, doesn't the tick have to bite you ?

You frequently find a tick crawling on you after a walk
in the woods around here, but you tend to notice it before
it bites you; pulling one out of your skin is something
you're not likely to forget.

Can you get the fever without it biting you ?  Do they
sometimes bite you and then let go so you don't realize
you were bitten ?  I know they will let go once they've had
their fill, but you certainly would notice this (arggh).

So how do you get the fever if you never pulled a tick
off yourself (as opposed to finding one merely crawling
on you) ?

John Eyles