A small town in S. America had been plagued, thousands of people were dying of yellow fever. The task was to find the cause and eradicate it. Two approaches used were: Microscopic research on the victims. Blood, flesh, and organs were scrutinized with care; clothing, linens and personal effects were analyzed but all to no avail. The second involved a massive effort to clean up the dirt and filth in the town. An effort that resulted in the cleanest and most sanitary town ever, but people were still dying of yellow fever.

**Explain what you think is wrong and how the problem can be solved.