Climate Change: Communicating Complexity
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The influence of weather on infectious diseases has been recognized for centuries. In our own experience, we know that some diseases like influenza are more common in the winter or others thrive better in the tropics. The effects of climate – weather over long periods of time – on infectious diseases have been getting a lot of attention lately. I was recently interviewed for a Focus Earth episode on infectious diseases and climate change. The introductory clip frames a debate between a calculated scientific position for the impact on individual infectious disease versus broad generalizations about global warming. It makes for great television and offers an opportunity to educate and engage the public about the health impact of climate change. In this case, both positions are true but highlight the difficulties in communicating the complexity of health effects from climate change – especially when we try to isolate the effects of climate from other biologic, ecologic, or social changes that lead to changes in infectious diseases.
There is no doubt that a dramatic increase in global temperature will cumulatively have a profound negative effect on health. This impact will be from a combination of factors including direct heat effects, increase in rainfall, extreme weather events including droughts and floods, and changes in air quality. There will also be changes in climate-sensitive infectious diseases such as zoonotic, vector-borne, environmental (fungi), and food/water borne diseases. These effects are most likely to be felt in tropical and semi-tropical countries which are least likely to be able to adapt to the changing climate. However, specific predictions about individual infectious diseases requires both 1) more information on the impact of climate and the geographical distribution of existing diseases, reservoirs, vectors, and pathogens which are all interconnected (for more information about infectious diseases at the interface of people, animals, and the environment, check out: www.cdc.gov/nczved/framework/); and 2) the ability of individual communities to adapt to these changes.
The need for better information to drive prediction and preparedness activities cannot wait. The effects of recent climate change are already evident in the northward presence of Vibrio vulnificus infecting oysters in Prince William Sound, the tropical Cryptococcus gattii fungal infections in the Pacific Northwest, expansion of tick-borne encephalitis in Sweden, and suggestions of shorter respiratory syncytial virus seasons in the United Kingdom. For more on CDC’s climate change activities visit Climate Change and Public Health. Please also share your thoughts.
2 comments on “Climate Change: Communicating Complexity”
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My question is how this climate change will affect the infectious diseases of our wildlife. I am an avid hunter and I operate a blog called
Coyote Hunting Resource that gives advice on hunting. I often eat the meat that I harvest and it would be good to know that I am not eating meat with some kind of fungal infections.
As a hunter, the kinds of risks you face will probably remain pretty much the same. However, those risks may increase or decline, depending on your location. So although you may not have to prepare for new risks, you should redouble your efforts to protect against known risks. Here are some examples of simple things you can do:
Insects and Other Arthropods
The risk of some diseases spread by mosquitoes, ticks, and fleas will probably increase in some hunting areas due to improved habitat for those bugs. Your best bet is to stick with standard low-tech precautions: use mosquito and tick repellents, wear protective clothing, tuck your pants into your socks, regularly inspect yourself for ticks and remove them immediately.
Rodents
Some diseases might become more common in areas where rodent populations grow as a result of changes in temperature and rainfall patterns. For example, incidence of Lyme disease and hantavirus pulmonary syndrome could increase in many areas of the United States, as could the risk of plague in the western section of the country. If you stay in remote cabins that are used only during hunting season, you might want to consider taking inexpensive steps to safeguard the cabin in order to decrease your risk for getting diseases spread by rodents (as well as insects and arthropods). For example, make sure all doors and windows have screens, and stop rodents from entering the cabin by patching holes around pipes and sealing any spaces under eaves, around foundations, and around doors and windows (see: http://www.cdc.gov/rodents/ for additional details).
Water
Because hunters also are at risk for waterborne diseases such as leptospirosis, it’s a good idea to avoid walking through standing water without protective rubber boots. This risk may increase as rainfall patterns change in some areas. Incidentally, increasing rainfall is likely to increase how often exposed water sources, such as streams, are contaminated. So always treat water before drinking it.
Field Dressing
When you handle and dress the kill, you need to be aware of the risk for contracting diseases like brucellosis, tularemia, and plague. These diseases will remain a risk for hunters, regardless of climate change. As a hunter, you can take simple precautions: Wear protective clothing and rubber or latex gloves while cleaning animals. Wash contaminated clothing, knives, and other instruments. Shower as soon as you can after returning from a hunting trip. Quickly clean any cuts or abrasions you acquire while cleaning animals, and take special care to avoid letting any part of the carcass or fluids from it come into contact with your broken skin.
Eating Game
The common foodborne illnesses associated with eating game are perhaps the easiest to avoid. Wash the game before cooking it, and make sure that it is completely cooked before eating.
In closing, predictions of how climate change will affect wildlife are largely speculative. We know that changes in climate variables will result in changes in the suitability of habitats for individual species. This will result in range shifts, changes in community structure, and changes in the abundance of species populations as competitors, predators, and prey, and also disease vectors become more or less abundant. These changes will influence how frequently these creatures have contact within and across species and how frequently they have contact with vectors. As you can imagine, this web of relationships is quite complex, and ultimate outcomes are extremely difficult to predict.
The American Veterinary Medical Association has a very helpful website with many more details about specific diseases and precautions for hunters: (http://www.avma.org/public_health/zoonotic_risks/hunters_precautions.asp)