Describing a disease that can be transmitted from animals to humans.

Any disease that spreads from animals to people. The animals can range from tiny ticks to lumbering cattle.

A disease that infects humans but originally came from other animals. The genetic sequence of the COVID-19 virus is similar to a coronavirus found in bats, so that may be where this disease originated. It may also have passed through other species on the way to humans, like snakes. Some zoonotic diseases, such as Zika and malaria, cannot be passed from person to person without an animal host.