Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Zoonotic diseases are infectious diseases that can be transmitted between species (in some instances, by a vector) from animals to humans. It is believed that many modern diseases started out as zoonotic diseases. It is hard to be certain which diseases jumped from other animals to humans, but there is good evidence that measles, smallpox, influenza, HIV, and diphtheria came this way. The common cold, and tuberculosis may also have started in other species. Learn more about the various zoonotic diseases, their transmission, as well as symptoms, cures and vaccines of these often deadly diseases in the following pages.