The introduction of a new virus to the human population is one of the greatest mysteries an epidemiologist can hope to unravel.Some of the most common and deadliest human diseases are caused by bacteria or viruses of animal origin.In recent decades this trend has only increased, with an estimated 70 per cent of emerging and re-emerging pathogens coming from animals.
This includes avian flu, Ebola virus disease, influenza, leprosy, lassa fever, MERS-CoV, rabies, SARS, smallpox, tuberculosis, Zika fever and other well-known diseases.How an infectious disease crosses the animal-human barrier is a riddle that can take years to solve.