At one time it was a very miserable valley, a swampland conducive only to breeding malarial mosquitoes.
The locals used to suffer regular outbreaks of disease due to the high mosquito population.
mnli hypothesis: The locals used to suffer regular outbreaks of disease due to the high mosquito population. premise: At one time it was a very miserable valley, a swampland conducive only to breeding malarial mosquitoes.