Final answer:
The flush toilet was key to improving urban sanitation and public health, evidenced by London's reforms after the Great Stink. Joseph Bazalgette's work on sewer systems helped prevent disease outbreaks, and global efforts continue to eliminate open defecation.
Step-by-step explanation:
The invention of the flush toilet was a significant advancement in sanitation that changed how cities managed human waste. Before its widespread adoption, cities like London faced severe sanitation issues that culminated in events such as the Great Stink of 1858. This crisis highlighted the urgent need for improved sewer systems and led to reforms initiated by Joseph Bazalgette, who was later knighted for his contributions to revamping London's sewage disposal methods.
With the construction of new sewer systems in the late nineteenth and early twentieth centuries, other cities followed suit, resulting in improved public health. These advancements helped reduce the incidence of diseases like cholera and typhoid fever. Despite the progress made, challenges still remain globally, as indicated by the United Nations' call to action to eliminate open defecation by 2025, with the current trajectory aimed at achieving this goal by 2030.