Dengue, Lyme and cholera: how climate change is driving the disease

On Monday, the Intergovernmental Panel on Climate Change issued a stark warning that time is running out to adapt to climate change. Climate change is already having “widespread and pervasive impacts” on people around the world, according to a new report by the scientific group, due to the warming that has occurred so far – about 1.09 degrees Celsius (1 .96 degrees Fahrenheit) above the pre-industrial era. levels.

Global warming isn’t just affecting humans by altering the weather and melting ice caps, the report warns. It also has resounding implications for how insects and other organisms move around the world, mix and spread disease to human populations. “Risks of climate-sensitive food-, water-, and vector-borne diseases are projected to increase at all levels of warming,” the report said. (Vector-borne diseases are those spread by blood-sucking insects like ticks and mosquitoes.) Additionally, the warming that has already occurred has already caused unprecedented disease impacts across the globe. Climate change is no longer a prospect of the future; It’s making people sick right now.

“One of the most striking findings of our report is that we find that the negative impacts are much more widespread and much more negative than predicted in previous reports in the current 1.09 degrees we have,” Camille Parmesan, author The report’s main coordinator told reporters on Sunday. “Some of the things we’re seeing that weren’t expected at 1.09 degrees are diseases emerging in new areas.”

Insects and other disease-carrying organisms spend much of their lives in one place, which is why some diseases are endemic to specific areas. Lyme disease, for example, is a disease transmitted by blacklegged ticks – tiny, eight-legged blood-sucking creatures that live in the northeastern United States and other parts of the northern hemisphere. . But climate change is disrupting the environmental factors that geographically limit these ticks. Warming temperatures and changing weather patterns in the United States are making it easier for ticks to proliferate and move to new areas, where the people and doctors treating them are unfamiliar with Lyme disease. It’s a double whammy, report says: Ticks are preying on larger parts of the population and increasingly common where they already live. “Climate change can be expected to continue to contribute to the geographic spread of the Lyme disease vector,” the report said.

Similar stories are unfolding in every corner of the world, as diseases emerge in places where they have never been found before. Dengue fever, a mosquito-borne tropical disease that causes fever, headaches and vomiting and has a 20% mortality rate if it progresses and is left untreated, is expected to become an increasing risk. more important for people in Asia, Europe, Central and South America. , and sub-Saharan Africa as warm seasons lengthen and Aedes aegypti mosquitoes expand their geographic range. “Billions more people are estimated to be at risk of contracting dengue later in the century,” said Kristie Ebi, a University of Washington epidemiologist and co-author of the report, on Sunday.

Other mosquito-borne diseases such as Zika virus, Chikungunya disease and West Nile virus are likely to become more common as climate change accelerates. The same goes for serious waterborne diseases such as vibriosis and cholera, which cause nausea, diarrhea and vomiting. Diarrheal diseases have declined globally thanks to better drug distribution and low-tech medical interventions like treating patients orally with a mixture of water, glucose and salts, but the report notes that increased rainfall and flooding in many areas has led to an increase in the occurrence of diarrheal diseases such as cholera and other gastrointestinal infections.

And if existing diseases aren’t scary enough, melting permafrost and coastal erosion could surface in prehistoric graveyards, campsites and reindeer graveyards in the Arctic, triggering ancient diseases against which modern humans don’t. have no immunity.

The report’s authors said it is extremely difficult to put a figure on future climate-related deaths, but they predict 250,000 additional deaths per year from heat, undernutrition, malaria and diarrheal diseases combined by 2050 Hundreds of existing diseases and others that will emerge in the coming years will add to the death toll.

Reducing the burden of disease on people is possible, but time is running out to make the necessary adjustments, the report says. The development of surveillance systems for vector-borne diseases, the implementation of early warning systems to alert communities to these diseases and the prevalence of new vectors, and the development of vaccines to inoculate people against vector-borne diseases are all essential additions to the preparation toolbox. To adapt to water- and food-borne diseases, the report recommends that governments improve access to clean water and protect water supply and sanitation systems from flooding. And protecting and preserving wild spaces such as wetlands, peatlands and forests from human development has the dual effect of sequestering carbon dioxide and preventing the spread of disease to humans by limiting contact between wild animals and animals. humans.

Zak Smith, director of the wildlife division of the Natural Resources Defense Council, who was not involved in the IPCC report, told Grist that governments are generally unprepared to take the necessary steps to protect health. public of the increased risk of disease due to climate change. . “What’s happened with COVID doesn’t increase my level of confidence that people are ready to make the kinds of investments that we need,” he said. “I think COVID is a warning. We don’t have that.

Teresa H. Sadler