What insect is known to transmit diseases by feeding on human waste and then on human food?

The insect that is known for transmitting diseases by feeding on human waste and then on human food is the cockroach. Cockroaches are scavengers that often inhabit unsanitary environments, including areas where there is human waste. They are adept at spreading pathogens because they can carry bacteria and viruses on their bodies and in their feces. When a cockroach moves from a contaminated area, such as a sewer or garbage, to a food source, it can transfer these pathogens, potentially causing foodborne illnesses in humans.

In contrast, while flies are also known for being carriers of diseases due to their ability to land on unsanitary surfaces and then food, the question emphasizes those insects that specifically feed on human waste before contaminating food. Ants and fleas do not typically have the same associations with human waste and food contamination in the context of disease transmission. Therefore, the cockroach stands out as the insect best characterized by this specific mode of disease transmission.