Author: Barry Schoub, Emeritus professor of virology, Wits University, University of the Witwatersrand

COVID stunned the world with an unanticipated pandemic. Now mpox, a disease which originated in animals, has been declared a global public health emergency. In this edited extract from his new book Fighting an Invisible Enemy, virologist Barry Schoub, the founding director of South Africa’s National Institute for Communicable Diseases, looks at how diseases spread from animals to humans. The introduction of ‘new’ diseases to humans Epidemics and pandemics of new diseases arise in two stages. Firstly, the zoonotic spillover event introduces the infectious organism, in the main a virus, into the human population from an animal source. The second…