The law in Washington, RCW 70.245, redined "terminal illness" as
an incurable and irreversible disease that has been medically
confirmed and will, within reasonable medical judgment, produce death
within six months.
California law and Hawaii law say the same thing
In Oregon, under ORS 127.505, the relevant term is "terminal condition", defines as
a health condition in which death is imminent irrespective of
treatment, and where the application of life-sustaining procedures or
the artificial administration of nutrition and hydration serves only
to postpone the moment of death of the principal.
The law of The Netherlands is less restrictive, and does not involve "terminal" conditions. The most relevant condition from article 2 is that there must be a finding that "the patient's suffering is unbearable with no prospect of improvement" (plus, there are informed consent and a second opinion standards to be met). The Canadian law in §241.2 requires that "they have a grievous and irremediable medical condition". That means, specifically, that
(a) they have a serious and incurable illness, disease or disability;
(b) they are in an advanced state of irreversible decline in
(c) that illness, disease or disability or that state of decline
causes them enduring physical or psychological suffering that is
intolerable to them and that cannot be relieved under conditions that
they consider acceptable; and
(d) their natural death has become reasonably foreseeable, taking into
account all of their medical circumstances, without a prognosis
necessarily having been made as to the specific length of time that
they have remaining.
Simply having been exposed to a virus, or even contracting the disease AIDS, does not qualify under the law. At later points in the progression of the diseases, it could – depending on jurisdiction.