Often, "hypotheticals" are used in science when direct experimentation
can't be done (or is not allowed, due to "ethical" considerations).
Because so many "HIV/AIDS" advocates like to cite studies, rather than
explain exactly what they are claiming (and in many if not most cases,
the findings of the studies contradict their arguments), the
hypothetical may be a way of "teasing" basic information and crucial
out of them.

Here is the hypothetical:  let us assume that there is a new
"disease," and the scientific investigators believe that a virus is to
blame.  They insist that the disease must be caused by one virus and
nothing else.  What would they have to do, exactly, to demonstrate
that they are right, in a way that adheres to the scientific method?