Which of the following diseases is NOT spread by flies and mosquitoes?

Giardiasis is a waterborne disease caused by the parasite Giardia lamblia, which is commonly transmitted through contaminated water rather than by insects such as flies or mosquitoes. This distinguishes it from the other diseases listed, all of which are spread by these insects.

Malaria is transmitted by female Anopheles mosquitoes; yellow fever is also spread by mosquitoes, specifically Aedes aegypti; and dengue is transmitted by Aedes mosquitoes. These vectors play a critical role in the life cycles of the pathogens responsible for malaria, yellow fever, and dengue, making them significant public health concerns in regions where these diseases are prevalent. In contrast, understanding that giardiasis is not associated with insect vectors is crucial for recognizing the different transmission routes of various infectious diseases.