Gastroenteritis-Can it last 4 weeks if you already have IBS?

Posted By Neal on January 11, 1999 at 11:55:23:







On Dec 11th, 1998 I came down with stomach flu/food poisoning type symptoms that included severe liquidy type diarrea (diarrhea), followed by vomiting, diarrea (diarrhea) again more vomiting and then a 102.5 fever that lasted for a day and a half.  The few days after this initial episode I had a 99 degree fever and loose bowel movements every few days but not to the degree I had during my initial attack on the 11th.  While the vomiting did stop after the first day, I have had bad nausea almost all of the time and a complete lack of appetite from Dec 11th until today (Jan 10), leading to the loss of 10 pounds.  My bowel movements have ranged from perfectly solid to loose during this time as well.  I am following a very low fiber (Brat) type diet hoping that it will ease my problems, but it is not helping at all.
I have suffered from IBS for many years but I have had it under control for a long time, and these symptoms and problems are not even close to anything I have experienced from my IBS in the past.  I have seen two Gastroenterologists and both said I am suffering from Gastroenteritis that is complicated by the fact that I have IBS.  I have had 3 stool samples tested and they are all negative for bacteria and ova/parasites.  I have also had a blood test and urinalysis done and nothing seems to be abnormal there either.
Is it possible to have Gastroenteritis for 4 weeks?  Everything that I have read from the medical literature on the internet/library states that Gastroenteritis clears up after 48 hours to a week.  If i had a bacterial or viral infection is it possible that I still have some of that lingering in my body after the intial episode 4 weeks ago.  I am concerned that something more than Gastroenteritis is going on here.  Any input or suggestions would be appreciated.