Future disease burden due to the rise of emerging infectious disease secondary to climate change may be being under-estimated

Climate change is predicted to increase the risk of the emergence or re-emergence of infectious diseases. Most, if not all, studies that have explored the possibility of diseases spreading into naive populations have only considered incidence as a measure of disease burden. We argue that, for many diseases, disease severity will be greater in previously unexposed populations than in populations where the disease has been endemic. There have been many examples throughout history of diseases becoming more lethal as they spread into new populations. A classic example of this is the impact on North Americans after the arrival of Europeans. A more recent example is the emergence of Zikaviruses in South America. There are a range of possible explanations for this phenomenon, including the age at first exposure, immunity, and host genetic factors. We need to plan not only for an increase in the incidence of a range of infectious diseases, but also for an increase in the disease burden.