Explain how Akeer’s laugh “was like music.” What caused her illness? Is the solution within the means of the family?

A Long Walk to Water is a 2010 historical fiction novel by Linda Sue Park about the Second Sudanese Civil War, which lasted from 1983–2005. It fictionalizes the story of Salva Dut, a boy who grew up in southern Sudan during the war. After being forced to leave his village at age eleven, he journeyed across Sudan, eventually leading over 1000 of the Sundanese Lost Boys to a refuge camp. Eventually, he is adopted by an American couple and finally reunites with his father. Salva Dut would go on to found Water for South Sudan, a nonprofit that helps ensure access to clean for water for citizens of South Sudan. 
Akeer is the five-year-old sister of Nya, a girl who must walk eight hours each day to find fresh water (hence the name of the novel). Akeer suffers from an intestinal disease, an unfortunate consequence of the status of water in Sudan. After taking Akeer to a doctor, she is treated, and when she is cured of her infection, her laugh is "like music," demonstrating that she's feeling better. Her illness was transmitted through the water. The prevention of future infections is relatively simple and accessible—the water will need to be boiled to kill any bacteria in it—but water is so scarce that it is a risk to boil it. When water is boiled, a portion of it evaporates, and supplies are so scarce to begin with.