The Deadly Dozen
If you look on the bright side, when you think of the health effects of climate change you probably think of fewer sub-zero spells and, therefore, fewer cold-related illnesses and deaths. Maybe. But in a warmer world, as I wrote last year, poison ivy and ragweed will get more prevalent and more toxic, and tropical diseases such as malaria and dengue fever will reach toward the poles. Those, it turns out, are only the tip of the (melting) iceberg.
This morning, the Wildlife Conservation Society released a report listing 12 disease-causing microbes that threaten to spread into new regions as a result of climate change. What does a wildlife organization have to do with this? By monitoring wildlife, scientists will be able to detect these spreading pathogens before they cause a human epidemic. Or so they hope. As Steven E. Sanderson, President and CEO of the WCS, said, “The health of wild animals is tightly linked to the ecosystems in which they live and influenced by the environment surrounding them, and even minor disturbances can have far reaching consequences on what diseases they might encounter and transmit as climate changes. Monitoring wildlife health will help us predict where those trouble spots will occur and plan how to prepare.” Think avian flu which, with other livestock diseases that have reemerged since the mid-1990s have cost the global economy an estimated $100 billion.
The report’s “deadly dozen”:
Avian influenza: The highly pathogenic H5N1 strain is deadly to domestic and wild birds, as well as humans, and could evolve into a strain that can spread from human to human. Climate changes such as severe winter storms and droughts can disrupt normal movements of wild birds, bringing avian flu to new regions and bringing domestic birds into greater contact with wild, disease-harboring ones at water sources if rainfall declines.
Babesiosis: Becoming more common in humans in Europe and North America as climate change alters the distribution of the ticks that transmit this disease.
Cholera: This water-borne diarrheal disease, caused by the Vibrio cholerae bacterium, is highly temperature dependent, so rising global temps are expected to increase its incidence.
Ebola: Outbreaks of this hemorrhagic fever (and the related Marburg fever) are related to unusual variations in rainfall/dry season patterns, which climate change disrupts.
Intestinal and external parasites: Their prevalence is expected to rise as temperatures and precipitation levels shift.
Lyme disease: As tick distributions shift as a result of climate change, Lyme disease will reach new regions.
Plague: One of the oldest infectious diseases known, it is spread by rodents and their fleas, whose distribution will change with shifts in temperatures and rainfall.
“Red tides”: These algal blooms are deadly to both humans and wildlife, and may become more common as the climate changes.
Rift Valley Fever: Potentially fatal in people, it is carried by mosquitoes, which threaten to reach into cooler climes and proliferate as the world warms.
Sleeping sickness: Trypanosomiasis is caused by a protozoan and transmitted by the tsetse fly, whose distributions could change as climate does.
Tuberculosis: The bovine form exists worldwide, infecting humans in southern Africa through the consumption of un-pasteurized milk. Droughts caused by climate change are likely to increase the contact of wildlife and livestock at limited water sources, increasing transmission of the disease between livestock and wildlife and livestock and humans.
Yellow fever: The disease-causing virus is also carried by mosquitoes, which will spread into new areas as temperatures rise and precipitation patterns shift.