Different story in cities. Urbanites rarely encounter wild animals, let alone infected individuals – their immunity is low. And cities are densely populated. So, once you have an increase in trade, meaning more individuals and species being sold, and the trade enters urban areas, the risk of exposure and potential for spread increase.
Now, back to the link between urbanisation and affluence because it promotes aviation and other forms of long-distance travel. As we have seen with COVID-19 (and SARS before it), it was overseas travel from China that initiated global spread. Or in Brazil, some of the first clusters were at elite urban country clubs, whose patrons had brought the virus back with them as they returned from traveling abroad. Of course, now the virus is spreading in the favelas, or slums, revealing another, social-justice, twist in the urban ecology story of COVID-19 – perhaps one for a later post.
For more on the link the wildlife trade and emerging infectious diseases, check out this paper and for the results of a modelling approach to understanding the link to urbanisation, see this one.