Which of the following is a vector for disease transmission?

Mosquitoes are a well-known vector for disease transmission. A vector is an organism that does not cause disease itself but spreads infection by conveying pathogens from one host to another. Mosquitoes are particularly significant in the transmission of several serious diseases, including malaria, dengue fever, Zika virus, and West Nile virus. They carry the pathogens that cause these diseases in their saliva and can efficiently transmit them to humans and animals during feeding.

In contrast, bacteria, fungi, and viruses are types of pathogens themselves. They can cause diseases directly but do not serve as vectors. Bacteria and fungi can be transmitted through various means, such as direct contact or via contaminated surfaces. Viruses require a host to replicate and are transmitted through bodily fluids, direct contact, or vectors, but they do not function as vectors. Therefore, among the options provided, mosquitoes stand out as the primary agents that facilitate the transmission of diseases without being the pathogens themselves.