Then there are the variables for private systems. How close is the drinking water well to the neighbors’ septic system. Is there a different water source for lawn and garden watering. How deep is the well and where does that water come from.
What about the gray water running out onto the lawn or garden? Will any food being garden grown become contaminated. Of course, germy hands picking it and tending a garden would contaminate the food. How germy is the dishwashing and clothes washing water?
This also means that public restrooms are probably laden with it at airports.
I will venture this is how the American tourist who had a 2hr layover in Wuhan got it.