Gastroenteritis ?

Hi -

For the past four and a half weeks, I've had some sort of gastroenteritis - the first few days I came down with it, I had constant diarrhea, low grade fever, chills, dizziness, nausea, and excessive gas/belching/stomach gurgling, severe stabbing pains in the stomach area.. after the first few days, the symptoms became less severe but become somewhat chronic - I have diarrhea every day, which occurs primarily in the morning shortly after I get up - sometimes for only a couple hours, sometimes until about noon or so - I feel progressively better during the day, although my stomach is bloated, gurgling very loudly with excessive gas, along with very slight afternoon fevers/chills and extreme fatigue all the time (sometimes dizziness too, although that seems to be mostly gone). It seems to go through cycles where for a few days the symptoms will get better, to the point where the diarrhea is almost gone, then the next day it will be back worse than ever. (The diarrhea is just excessively watery, no blood or mucous or unusual colors to it). I still experience upper abdominal pain (sharp, in the stomach area) but in the lower abdomen just slight cramping (generalized) which persists throughout the day as well. I've lost a ton of weight, too, even though I'm trying to still eat normally.
The strange thing is that I know of at least eight different people who all are experiencing the exact same symptoms (right down to the time of day the symptoms occur) who have not recovered yet either. Three of them are co-workers, one is a neighbor, and two work in my OB/GYN's office, others are people I've met in passing, either patients at my office or spouses of friends.. One of them has had it for a week, one has had it for 3 months, the rest are around a month or so. And I must stress they are the EXACT same symptoms. Same morning watery diarrhea, afternoon fevers/chills, sharp stomach pains and generalized cramping, gas/bloating/gurgling and cycles where they feel they are getting better and then get worse again. Everyone in my office came down with it within days of each other (but no one got sick at exactly the same time).
I do not spend any time with any of these people outside of work, we never eat the same food or go out to eat together, (we all have very different diets and bring our own lunches) or drink the same water. Most of us live in very different areas, different counties even (we're all in upstate NY). Most of the people who are sick also have mentioned that their spouses are also sick with it.
I have tried Imodium, Kaopectate/Pepto Bismol, probiotics, fiber (Equalactin and Citrucel, tried small and large doses), and the BRAT diet - no effect whatsoever. Even when I avoided food for 24 hours and drank nothing but water the symptoms were the same. It doesn't seem to be affected by medication or by what I eat or don't eat.
I have been tested for every food allergy possible - including lactose intolerance and both blood tests and biopsies for Celiac's - all negative. My basic blood work (blood sugar, CBC) was fine. I have also had a colonoscopy and an ESR blood test to rule out Crohn's, ulcerative colitis, diverticulitis, etc. - all fine. No immune deficiencies either that we can find.
I have not been out of the country or even out of the state in 10 years, (even 10 years ago I only visited Italy) and don't know anyone else who has recently. I also don't have any other medical conditions, haven't received any transfusions, etc. I don't have kids, I live alone.
My doctor is perplexed as there are other people with the same symptoms. She says it sounds like a parasite, but they're typically not THAT easily transmitted person to person, and we can't find any common food we may have all eaten, water or daycare centers we may have all been commonly exposed to. (I buy bottled water, my co-workers either have well water or filtration systems at home, my neighbor drinks well water.) No one drinks the water at work. And while I do work in a dental office, and am exposed to a lot of patients throughout the day, we're all impeccable about hygiene, handwashing, etc., and everything is up to OSHA standards.
Is there any type of bacteria/virus/parasite that could be transmitted easily person to person that you know of that could cause such prolonged symptoms? Are there any other tests you could suggest? I am going to have a stool culture done, but are there any specific parasites or bacteria I should ask them to test for that they may not test for routinely? Would it be beneficial to ask for a referral to an infectious disease specialist? Like I said, my doctor is stumped, I'm already seeing a gastroenterologist who is also stumped - he said he'd call it IBS except that other people are experiencing the same thing. My neighbor with the symptoms did turn in a stool sample which was apparently "negative for bacteria and parasites" but I don't know exactly which ones they tested for. We've talked about testing for Hep A and maybe even Hep C - could this be a concern, even though no one has gotten jaundice and it's not spread by casual contact? (Everyone in my office is vaccinated against Hep B).
Oh, and I don't know if this is significant, but three of the people I work with have had pets with recurring diarrhea which have been treated with Flagyl for a "bacterial infection". None of these people are sick, though.
Any suggestions would be appreciated by me, my co-workers and my doctors! Thanks!!