A zoonosis is an infectious disease that can be transmitted from animals to humans. The pathogen may be a virus, bacterium, parasite, fungus or prion, and transmission can occur through direct contact, contaminated food or water, an insect or tick vector, or airborne routes. A large proportion of known human infectious diseases, and the majority of newly emerging ones, are zoonotic in origin.
The concept matters because it changes where prevention has to happen. Controlling a zoonosis often means intervening in animal populations, food production or the environment rather than only in human healthcare.
Several drivers push animal pathogens into human populations: expansion of agriculture into previously wild areas, intensive livestock farming, wildlife trade, deforestation and habitat loss, climate change altering vector ranges, and the speed with which international travel moves an infection once it has crossed over.
One Health is the framework recognising that human, animal and environmental health are interdependent and cannot be managed in isolation. In practice it means veterinary and human public health surveillance systems that share data, coordinated antimicrobial stewardship across human and agricultural use, joint outbreak investigation and shared laboratory capacity. Rapid diagnostics and genomic sequencing have become central to this work, allowing an organism found in a patient to be matched against isolates from animals or food and the source traced.
.svg)
