Vectors are organisms that carry pathogens from one host to another.
Pathogens in biosolids may pose a disease risk when in contact with humans or other susceptible hosts. Vectors include flies, mosquitoes, rodents, pets, and birds. Vectors can transmit pathogens to humans through direct contact such as bites. Generally biosolids do not provide an attractive environment for flies, rats, or birds. These creatures are attracted to a food supply, pungent odors, a comfortable habitat, or a water source.