There seems to be a focus on illness in this novel, which reflects Jane's Austen own health at the time she wrote Sanditon. 5 days after Austen finished chapter 12, she wrote a letter in which she explained that she was very ill and reflected that “Sickness is a dangerous Indulgence at my time of Life”

http://www.bbc.com/culture/story/20170714-the-jane-austen-novel-you-dont-know