Salva is a real person (the story is based on him) while Nya is a fictional character.
The paragraph expands on the central idea that malaria was a deadly disease in Elizabethan England. However, it explains Elizabethan misconceptions about the spread of malaria.
Answer: We don't truly know, but we know by scientific and religious data that was gradually developed by a force (it could be nature force or a force of some God)
