Why southern China is a hotbed for disease development

Pandemics like Zika and Ebola can originate in one continent and quickly spread to another. To stop outbreaks before they start, scientists are trying to identify regions conducive to the development of new disease. One target is southern China, where factors such as daily wildlife trade and sewage-filled rivers have repeatedly led to the rise of new viruses. Hari Sreenivasan reports.