I have the flu virus & a fever. I'm not sure if it is the swine flu or not.

The job interview is at a nursing home and I know that the elderly are very susceptible to diseases. I also don't want to get the interviewer sick either. just in case the flu would spread all around the facility

Would it be ok for me to reschedule the interview a week later when I would have recovered?
the interview is tomorrow...so I should call today?

I would leave that decision up to those who will conduct the interview. Just explain your situation and ask them if they would rather reschedule or not. If you go, I would wear a surgical mask.
You may gain points with them if you use this approach.

It would technically be OK to reschedule, but you should also make sure that you are giving the interviewer as much notice as possible. Don't wait until the morning of the interview to call and say that you're not feeling up to it, the flu doesn't happen overnight.