Infectious diseases that have spread from animals to humans.  Zoonotic pathogens (germs) may be bacterial, viral or parasitic, and can spread to humans through direct contact such as touching an infected animal,  eating contaminated food, drinking unclean water, or in the natural environment.

They represent a major public health problem around the world due to our close relationship with animals in agriculture, as companions, and in the natural environment. Urbanization and the destruction of natural habitats increase the risk of zoonotic diseases by increasing contact between humans and wild animals. Zoonoses can cause disruptions in the production and trade of animal products for food and other uses. According to the WHO:

  • There are over 200 known types of zoonoses
  • Zoonoses comprise a large percentage of new and existing diseases in humans
  • Some zoonoses, such as rabies, are 100% preventable through vaccination and other methods 

Other examples of zoonotic diseases include avian flu, SARS, MERS and Ebola. COVID-19 is regarded as a zoonotic disease, most likely originating in bats (though this is not yet confirmed) and possibly passing on to humans through an intermediate animal, thought to be the pangolin. The SARS-CoV-2 virus is suspected of spilling over or jumping from an animal to a human at a wet market in China.

Some zoonotic diseases do not affect animals but make people sick. According to the World Health Organisation, 61% of all current human diseases are of zoonotic origin, while 75% of newly discovered diseases are zoonotic. There is also reverse zoonosis, which is when infections are passed from humans to animals.



Infectious Disease


Wet marketSARS (severe acute respiratory syndrome)SARS-CoV-2MERS (Middle East Respiratory Syndrome)COVID-19One healthWHO (World Health Organisation)