According to the introductory paragraphs of "The Country of the Blind," how did the mysterious mountain valley first become cut off from the rest of civilization?

Check below for the explanation

Explanation:

Every inhabitant of the village in the mysterious mountain valley in Ecuador became blind due to the outbreak of a pandemic ( a virus). They quickly adapted to that lifestyle of being blind that they began to see sight as a source of craziness. This was evident from the way they humiliated Nunez who thought he could use his sight as an advantage to rule them. Their blindness made them disconnected from civilization and they saw it as a normal way of life.

the nurse was the one who kept interrupting the balcony scene.

romeo decides to spend the night with juliet before leaving verona due to being exiled for killing