Sorry Bodgy. It is way too complicated. It all has to be narrowed down according to the individual.
For example. A person gets a spider bite. Two years later, after completely forgetting about it, the person starts to have all the classic signs of candida.
Ten thousand dollars later, the person discovers, there is a toxin in his\her system that causes a build up of naturally produced Antibiotics
from the body [not to be confused with antibodies].
This killed off much of the natural commensal community of microbes in the gut, and dybiosis sets in.
That is just a fictional example, but many others exist.
The fact there are now genetically modified bugs out there, and chemical interactions with natural ones, airplanes bringing unknown bugs from country to country makes things very complicated.
Have you heard of airport malaria? Ya, mosquitoes of certain species that carry malaria, get aboard planes all the time. They end up getting out, giving malaria to animals, which transfer it to local mosquitoes and can give human strains back to humans in the area.
There are many weird examples of how infectious things get around.
So, to end the point simply; find a health consultant, try and get the right tests done according to your individual situation. Shroom