Zoonosis

Zoonosis or a zoonotic disease is an infectious disease which an animal can give to a human. These diseases may be caused by bacteria, viruses, fungi, or parasites.^[1]

Zoonotic diseases are very common. About 60% of all infectious diseases in humans are spread by animals.^[2]

Zoonotic diseases can be spread in different ways. They may be spread from a sick animal directly to a human – for example, through bites and infected saliva (like with rabies), or through the air. This is called direct zoonosis.

Zoonotic diseases can also be spread through a vector. This is an animal that carries the pathogen that causes the disease without getting infected. Diseases like this are called vector-borne diseases.

Sometimes the vector picks up the disease from another animal. For example, rats who have the bubonic plague do not directly infect humans. Instead, fleas bite the rats and pick up the bacteria that causes plague without getting sick. Then, if the flea bites a human, they can pass the bacteria on to the human, and the human can get the plague.^[3] The rat is the host of the disease, and the flea is the vector.

1. ↑ "Toxoplasmosis". One Health. United States Centers for Disease Control and Prevention. October 18, 2013. Retrieved February 11, 2016.
2. ↑ Taylor L.H; Latham S.M. & Woolhouse M.E.J. 2001. Risk factors for human disease emergence. Philosophical Transactions of the Royal Society B: Biological Sciences 356 (1411): 983–989. [1]
3. ↑ "Plague". WHO.int. World Health Organization. November 2014. Retrieved February 11, 2016.