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September 12, 2016

Responding To: The Challenge of Climate Change

Climate Change and Infectious Disease

Paul Roepe

Changes in climate have been linked to increased human disease for centuries. Additional significant and dramatic changes in climate will, over time, continue to lead to increasingly dramatic effects on human health. The most frequently discussed examples include increased incidence of vector-borne diseases such as malaria, as well as waterborne diseases such as cholera, however, it is important to note that changes in climate also alters air quality (which can then increase pulmonary disease and asthma), human migration (which is then often linked to severe mental stress and other health issues), and also increases other problems that impact human health. For example, an increased frequency and intensity of severe weather related events (hurricanes, floods, etc.) leads to significant increases in weather related injury and death. Virtually every aspect of human health is now increasingly affected by climate change. For vector-borne diseases such as malaria, dengue, and now Zika, climate change impacts insect vector habitats in profound ways, which then alters disease transmission and severity. For example, due to increased temperature and changes in rainfall patterns, mosquito larvae that transmit a range of viruses and parasites can now survive in habitats that were once inhospitable to these species, increasing their range and potential impact on the human population. It is likely that the world will continue to see newly emerging epidemics such as Zika, as well as an increased intensity in infectious diseases once thought to be vanquished, as these trends continue. Changes in rainfall patterns also increase the severity and likelihood of certain waterborne illnesses in key regions of the globe. Cholera is perhaps the most infamous in this regard, but cryptosporidiosis and leptospirosis have become much more troublesome in recent years, and it is also important to recognize the impact of altered water quality for crops and livestock, which then indirectly can have huge consequences for human health. All these trends, and other emerging problems are exacerbated by changes in climate. Modeling and predicting the precise increase, in, for example, malaria transmission due to a specific elevation in local temperature remains extremely challenging, whereas increases in cholera transmission due to specific rainfall events can be defined more clearly. As modeling of vector-borne diseases improves, and as the biology of infectious disease vectors and infectious microbes continues to advance, the scientific community will be able to make more definite infectious disease predictions for various regions of the globe. Arguably however, the most profound question for our time is can we afford to wait for those additional improvements in our predictive abilities before we act? Today, ongoing political posturing related to climate change denial, Zika vaccine funding, mosquito control programs, and other key elements for controlling infectious disease linked to climate change suggest that the challenges are likely to become more severe before they become more manageable. Increased education and committed action by the scientific community are desperately needed.

Paul D. Roepe is a professor of chemistry (main campus) and of biochemistry, cellular, and molecular biology (medical campus) at Georgetown University. His research focusses on analysis of drug resistance phenomena and the development of new drug therapy, principally for malaria and other infectious diseases.

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