What is fluxes?
Since you put this question in the literature section, I assume that you are asking what is meant when (in old works of literature) it is said that someone had "a flux."
If that is what you are asking, the answer is that it means that the person had some sort of illness and usually one that involved diarrhea -- so a disease such as cholera.
The word flux literally means to flow. Medically, it meant to have a lot of liquid flowing from your body. This is why it was generally used to describe diseases like cholera.
The noun 'flux' is an 'Uncountable Noun' which means it cannot have a plural 'fluxes.'
The meaning of the word is 'a flow or a continuous flow.'
It has different meanings in different fields.
In Physics, it would refer to the lines of force of an electric or magnetic field.
In Chemistry it refers to a substance that induces or aids flowing.
In Metallurgy it refers to a mineral added to the metals in a furnace to promote fusing.
In Medicine it refers to a large and uncontrolled fluid discharge especially from the intestines.
In Philosophy it refers to the state of constant change in which all things exist.