As carriers of diseases, urban pest birds pose a serious health threat to people. Nuisance birds promote the transmission of several hundred types of diseases, infections and illnesses.
Symptoms range from upset stomachs to serious diseases of the nervous and respiratory systems.
Bacteria, viruses and fungal agents thrive in environments where droppings accumulate in enclosed areas. These agents, in nests located near air-handling systems, become particularly hazardous. After the 1994 Northridge earthquake several hundred people came down with flu-like symptoms. It was found to be caused by people breathing in dust and airborne debris filled with histoplasmosis spores and related fungal agents. Bird droppings promoted their growth.