Giardia is an intestinal parasite that causes diarrhea (as I'm sure
Don't know how you respond to info like this, but the organism is
transmitted person-to-person via a fecal-oral route.
You probably have young children in your household? Children are
notorious for poor personal hygiene (i.e, not washing their hands,
or not washing them well enough). People who become infected with
Giardia do so by ingesting small particles of fecal material that
are contaminated by the organism. The fecal material comes from
another person who has grabbed a door knob, prepared and contaminated
food, shared contaminated food, etc . . .
As shocking as this may sound (not sure if it is for you, or not),
fecal-oral transmission of disease is a VERY common occurrence.
Also -- Giardia are water-born organisms. Humans can also get the bug
from drinking water contaminated by animal feces.
Have I answered your question?