Zoonotic diseases are the infectious diseases in humans, which are transmitted from animals to humans. They can be caused due to infectious agents such as prion, bacteria, parasites, or viruses. Zoonotic diseases can be transmitted directly from animal hosts to humans by media such as air or through saliva or bite of the host. The indirect transmission of zoonotic diseases occurs through transmission by intermediate species or vectors, which may carry the pathogen. The genetics of the host plays a significant role in determining which animal viruses have the capability to replicate themselves in humans. Those animal viruses which require less number of mutations for replicating themselves in the human cells are considered to be more dangerous. This book provides significant information to help develop a good understanding of zoonotic diseases. Also included herein is a detailed explanation of the hosts and vectors associated with zoonotic diseases. This book will prove to be immensely beneficial to students and researchers studying these diseases.