A zoonosis is an infectious disease caused by a pathogen that has jumped from a non-human animal to a human. Typically, the first infected human transmits the infectious agent to at least one other human, who, in turn, infects others. Zoonosis refers to diseases that can be passed from animals to humans. They are sometimes called zoonotic diseases. Animals can carry harmful germs, such as bacteria, fungi, parasites, and viruses. These are then shared with humans and cause illness.