Stress is often associated with the onset of CFS. While this is true, the impact of stress is the great suppression of the immune system. Bottom line is that the triggering event is an infection – which may be viral, bacterial or parasite. The actual infection symptoms may be mild and ignored.
There is a recent epidemic of CFS and IBS in Bergen, Norway that really illustrates the process well. It is unique because of all of the followup and availability to researchers of all of the patients records — something that is impossible in the US. Coupled with this was the immense oil wealth of Norway that resulted in money to burn on these patients.
Bergen, Norway is better than Incline Village!
In 2004, Bergen, Norway had a major epidemic of giardiasis and because of the national medical system, they were able to measure what actually happens and follow all of the patients through the years – something impossible in the US. They verified by lab tests that the giardiasis was successfully treated. They also found that infections of cryptosporidum parvum increased as a side effect. “One-third of the patients experienced recurring symptoms after treatment” 
So 1/3 did NOT return to normal within a year.
- At 2 years: “among 82 patients with persisting abdominal symptoms elicited by the Giardia infection…We found that 66 (80.5%) of the 82 patients had symptoms consistent with irritable bowel syndrome (IBS) and 17 (24.3%) patients had functional dyspepsia (FD)” 
- “Fatigue was reported by 41%, whereas 38% reported abdominal symptoms, and there was a highly significant association between these symptoms. Increasing age was a highly significant risk factor for fatigue. The symptoms were not due to chronic infection in this cohort.” at 2 years after the infection [1262 patients] 
- “Patients with post-giardiasis IBS suffer very little somatic comorbidity, suggesting that the aetiology of this form of postinfective IBS is predominantly biological in origin and may thus differ from the more common, non-postinfective forms of IBS.” 
- At 3 years, “The prevalence of IBS in the exposed group was 46.1%… Chronic fatigue was reported by 46.1%” 
- “A total of 58 (60%) out of 96 patients with long-lasting post-infectious fatigue after laboratory confirmed giardiasis were diagnosed with CFS … At the time of referral (mean illness duration 2.7 years) 16% reported improvement, 28% reported no change, and 57% reported progressive course with gradual worsening. ” 
This outbreak, like CFS, mainly affected females “Young women have previously been reported as the predominant group infected during a waterborne giardiasis outbreak, due to elevated water consumption. Here, the demographics of those subsequently infected are described, and young women again predominate. As secondary cases were not waterborne, this cannot be attributed to drinking habits.” 
In 2007, ” Both these findings subsided overtime. Increasingly, investigations could not determine a definite cause for the persistent symptoms. The very long-term post-giardiasis diarrhoea, bloating, nausea and abdominal pain documented here need further study.” and ” In conclusion, patients with Giardia-induced gastrointestinal symptoms developed both IBS and FD. They exhibited gastric hypersensitivity with lower drinking capacity and delayed gastric emptying.” 
Is giardia the source of CFS?
The answer is that it can be a cause of CFS in some. There appear to be many infections that can result in post-infection fatigue syndrome.
“Prospective studies have shown that 3% to 36% of enteric infections lead to persistent new IBS symptoms; the precise incidence depends on the infecting organism.” 
“All but one patient were diagnosed with IBS, 58% with severe symptoms. Extra-intestinal symptoms suggestive of chronic fatigue and fibromyalgia were demonstrated in 85% and 71%, respectively.“
What is striking about this epidemic is that the results matches the general population of CFS patients
- Mainly female patients (almost the same ratio of males to females – 86% female )
- 80% had IBS, this is also the rate with CFS in some studies
- Symptom improvement from tetracycline or the use of live faecal flora (quasi fecal transplant) occurs in both, and with both, disappears if not maintained.
- ” Nevertheless, short-term therapy with either antibiotics or probiotics does seem to reduce symptoms among IBS patients. It seems most likely that the benefits of antibiotic therapy are mediated through subtle and, perhaps, localized, quantitative and/or qualitative changes in the colonic flora.” 
Reports of two approaches to treatment parallel what has been tried with CFS, with similar results.
- A 2008 study on persisting symptoms after Giardia infection found that “tetracycline and folic acid for 28 days.. the improvement was significant for the T/F group…One month after treatment, in the T/F group (23.1%) .. reported global symptom improvement. Symptoms recurred in all of these, and after 1 y total symptom scores were unchanged from baseline”.
- “Eighteen received treatment with rifaximin plus metronidazole (8-10 days) whereas 10 received a suspension of live faecal flora, installed into the duodenum during gastro-duodenoscopy… total customary symptom scores were barely significantly reduced (p = 0.07) after antibiotics, but were highly significantly reduced (p = 0.0009) after bacterio-therapy. However, symptom improvement following bacterio-therapy did not persist 1 year later…. High faecal excretion of fat and SCFAs suggests that intestinal malabsorption of fat and carbohydrates may play a role in the IBS-like complaints of these patients.” 
Where do we go from here
The problem is that things can improve but do not persist, IMHO, the positive changes did not eliminate the issue, just suppress it. The duration of treatment need to be longer and it must be very aware of quick development of resistance of the infections (which are likely different than the cause) which may require both anti-bacteria rotation and probiotic rotation thru many different families (lactobacillus seems to be the least important one).
This site explores what we know and what we can do with the tools on hand.
Patient Description to Medical Professional:
“I have a dysfunctional *stable* microbiome that needs to be reset. There is a common pattern for IBS/CFS patients. There has been good success rate using a protocol originally developed by the Pasteur Institute consisting of rotating selected antibiotics that appears to reduce the very specific overgrowth. There is a challenge of repopulating the undergrowth which is not just the lactobacillus family – so typical probiotics are of very limited benefits. There has been good success (at least temporarily) with fecal transplants.
The key treatment challenge is that resistance to antibiotics often develop quickly, there are many species involved and the difficulty of kick-starting a healthy set of gut bacteria that are strong enough to keep the bad ones controlled.”
- [A modern epidemic]. 2004
- Cryptosporidium parvum infections in Bergen, Norway, during an extensive outbreak of waterborne giardiasis in autumn and winter 2004. 
- [Uncovering the giardiasis-outbreak in Bergen 2004]. 
- Effects of albendazole/metronidazole or tetracycline/folate treatments on persisting symptoms after Giardia infection: a randomized open clinical trial. 
- Persisting symptoms and duodenal inflammation related to Giardia duodenalis infection. 
- Subjective health complaints and quality of life in patients with irritable bowel syndrome following Giardia lamblia infection: a case control study.
- High rate of fatigue and abdominal symptoms 2 years after an outbreak of giardiasis.
- Antibiotic or bacterial therapy in post-giardiasis irritable bowel syndrome. 
- High rate of fatigue and abdominal symptoms 2 years after an outbreak of giardiasis. 
- Severity of Giardia infection associated with post-infectious fatigue and abdominal symptoms two years after. 
- Irritable bowel syndrome and chronic fatigue 3 years after acute giardiasis: historic cohort study. 
- Chronic fatigue syndrome after Giardia enteritis: clinical characteristics, disability and long-term sickness absence. 
- The impact of atopic disease on the risk of post-infectious fatigue and irritable bowel syndrome 3 years after Giardia infection. A historic cohort study. 
- Immunophenotyping in post-giardiasis functional gastrointestinal disease and chronic fatigue syndrome. 
- Chronic fatigue syndrome 5 years after giardiasis: differential diagnoses, characteristics and natural course. 
- Irritable bowel syndrome and chronic fatigue 6 years after giardia infection: a controlled prospective cohort study. 
- The relationship between irritable bowel syndrome, functional dyspepsia, chronic fatigue and overactive bladder syndrome: a controlled study 6 years after acute gastrointestinal infection. 
- Perceived food intolerance and irritable bowel syndrome in a population 3 years after a giardiasis-outbreak: a historical cohort study.