Dr. William C. Gorgas (1854–1920) brought the endemic diseases of Panama under control by destroying mosquito breeding grounds, virtually eliminating yellow fever and malaria. His work was probably more essential to the completion of the canal than any engineering technique.

A zoonosis is any infectious disease or parasitic disease of animals that can be transmitted to humans. Lyme disease and Rocky Mountain spotted fever, for example, are indirectly spread to humans from an animal through the bite of a tick. Common household pets also can directly transmit diseases to humans unless preventive measures are taken. Cat-scratch fever and toxoplasmosis may be contracted from cats. Wild animals and dogs can transmit rabies. However, most zoonosis diseases are relatively rare and can be treated once detected. Such sensible actions as regularly vaccinating pets and wearing long-sleeved shirts and pants when hiking can prevent the spread of most zoonoses.