Hello,
I also had some improvment after moving to other country. I was in moderate cfs for years after mononucleosis infection, i was hyperactive before the illnes, so despite the fact that my overall energy level decreased i was still far more active than typical person, living almost normally(i had ibs-like symptoms, temperature lower than normal, twitchings of muscles, maybe some other things that is hard to measure ).
All of the previously mentioned things were a bit anoying but there were not causing a huge dump in quality of my life. The only thing that was bothering me was problems with upper respiratory tract- every time that i was doing very drainning training sessions (sometimes i needed a few of them in a row to induce the problems) i got sick(at least i was thinking im getting sick).
Of course i had no idea that im having cfs, so i thought that training sessions reducing force of my immune system to such low level that im catching colds. What actually happened was probably was that high amount of pro-inflammatory cytokines(produced by pem not actually virus/bacteria infection) creating flu-like symptoms like headache, running nose, cough, etc.
Those infections were strange from the beging becouse there were no esr/crp increase or change in white blood cells and they last really short like 2 or 3 days maximum(what as i said- suggest that infection was not infection at all and was produced by cfs-agitated immune system )
So getting back to my story, I moved from northern Poland(near Baltic sea) to Malta(the island on mediterranean bellow the italy). 'Infections' disapeared imediatelly and i was training hard for about 3 years without problems, what is interesting when i was comming back to Poland for few weeks holidays i was always getting 'infections' even after one training. Nonetheless depite the fact i was living in Malta i slowly declined in general health, so im much worse overall but we wont ever know if i would decline faster in poland.
diffrences between distant places that i was thinking about:
atmospheric pressure
temperatures
humidity
'chemicals' in food
water from sewage system
diet paterns
behavioral/action paterns
pollens in air(becouse of diffrent plants)
species of mould inhabiting certain region
In my situation i don't see clear explanaiton, since i was living my life in malta really similar to one that i was living in malta(diet, behavior, lifestyle, etc) *inevitably there were some changes but its hard for me to unfold my whole life to single factors.
What is more i was living in around 4 apartments in poland and the problems were happening everywhere so i dont think it is mould. I dont think its temperature case becouse summers in poland are hotter than winters in malta and i still had problems during summers in poland and not during maltas winters.
Now that im back in poland i might try drinking botteled water (in malta water from sewage system was drinkable but not tasty at all, becouse of chlorine, so i was using only botteled water for everything whereas in poland i'm using tap water all the time), i will probably also try humidifiers to make air humid as its possible, as you can encounter in malta(which seems counterproductive because microorganisms tend to like humidity) i will update you on changes.