Flies typically breed in garbage, decaying flesh, excrement of animals and humans, sewers, compost piles, and any other place where matter is decaying. This enables them to pick up various kinds of diseases which can be transmitted to people by biting or by landing on food, where they can add bacteria and viruses to the food. Since flies are able to transmit disease so easily, it is necessary to get a fly exterminator quickly. The diseases that they can carry include malaria, yellow fever, encephalitis, and dengue fever.