I'm guessing that you went back to your usual mileage too quickly and if you're only planning on taking one week out with what you've posted, then I doubt that you'll reap much benefit.
If you really are struggling as much as you say, then it looks like you'll need more than a week and I'd also suggest a rethink of your training plans.
Whilst I appreciate your concern, you're not going to lose much after just one week off - and I'm sure that there are plenty of others on here who are forced to take a much longer break, so I'm not sure that you'll get a lot of sympathy for one week's absence.
If you really don't want to take time out, why not cut out some runs and take up some form of cross training instead, or, if you're using your HR, spend a week or two running at a low HR / recovery pace then reassess?
But as others have said, it's probably nothing more than the fact that it's taken longer than you assumed to get rid of the virus.
Edited: 02/12/2011 at 18:46