Climate change is in the news all the time these days, and for good reason. The Intergovernmental Panel on Climate Change (IPCC) report released earlier this year, which reflects the opinion of 234 experts from 195 countries, made for sobering reading. By 2040 we will cross a key threshold that will have catastrophic consequences for humanity.
This threshold is a 1.5°C increase in global mean temperature above pre-industrial levels. The report states, “It is clear that human impact has warmed the atmosphere, ocean and land.” It also noted that we are near a tipping point where we will have passed the point where we can reverse trajectory towards extremely negative consequences for life on Earth, including us.
More promisingly, the IPCC report lists a number of things we can do to ensure we don’t reach the tipping point and inexorable rise in temperature. We need to replace fossil fuels as soon as possible and switch to renewable energy sources. We also need to change our dietary habits as livestock farming is a major contributor to global warming. And thirdly, we must make our cities significantly more environmentally friendly. Each of these is very challenging, but there is no doubt about what needs to be done.
We are also all now familiar with what could happen if we don’t reverse global warming. There will be longer and longer periods of extreme weather that are very disruptive and damaging. Forests will also die, exacerbating global warming because trees are major carbon sinks. And we all know the risk of sea level rise due to melting ice caps, leading to widespread flooding, especially in poorer countries that are particularly vulnerable, leading to mass migration of people and all that entails.
However, there is another consequence of global warming, as if these problems are not enough to continue. You may be less aware of this, but it’s an important one. The incidence of a whole range of diseases will increase. With the increase in global temperatures, many infectious diseases have also erupted.
Mosquitoes are now thriving in areas where they had not previously and that is due to increased temperatures
Scientists have concluded that climate change has made more than 200 infectious diseases worse. In a report titled “More than half of known human pathogenic diseases may be exacerbated by climate change,” published in nature climate change, by lead author Camilo Mora of the University of Hawaii, they searched the scientific literature for evidence of how features of climate change, including rising temperatures, sea level rise and droughts, affect infectious diseases. These included bacterial, viral, insect and fungal infections. More than 77,000 reports were examined, with most studies published after 2000, when interest in this particular aspect of climate change began to grow.
What they found was startling. Climate change has made 218 of 375 infectious diseases worse. But it went beyond that, because they also found that non-infectious diseases such as asthma or venom bites from snakes and insects were also getting worse as a result of climate change.
Why could that be? The scientists found that the main reason infectious diseases are spreading more is that the pathogens come into contact with people more often. A good example is Lyme disease. This is a painful disease caused by tick bites. Ticks are tiny blood-sucking insects that usually jump onto us from small mammals or birds. When the tick bites, it transmits a bacterium called Borellia into us, which then causes an inflammatory condition similar to arthritis, but also causes severe fatigue and headaches that can last for months.
Lyme disease remains difficult to treat. As global temperatures rise, the animals the ticks live on can migrate to new habitats, bringing the disease with them. Lyme disease has now been reported as far north as Canada and even Nova Scotia in areas previously too cold for the ticks to survive. None of these locations had reported cases of Lyme disease prior to 2002.
There are many insect-borne diseases, not the least of which is malaria, which is transmitted by mosquitoes. They also thrive in areas where they had not previously due to increased temperatures. They have also been found to be active longer wherever they may be, with one study showing activity increased by 39 percent between the 1950s and the 2010s.
This almost doubles our risk of catching malaria from mosquitoes. We still don’t have a vaccine against malaria, although progress is being made. The mosquito is also the source of other nasty diseases with names like dengue fever and chikungunya. Higher temperatures have been found to increase the survival and bite rates of mosquitoes carrying the West Nile virus. This virus is rarely fatal but causes symptoms such as joint pain, headaches, vomiting and diarrhea.
And then there are bats. We are all all too familiar with the global catastrophe they caused when they were revealed to be the source of the SARS-CoV-2 virus that caused Covid-19. They are also encroaching into areas where they previously could not survive, again attributed to rising temperatures. This means a greater chance that they will encounter us and transmit viruses.
Overall, the evidence suggests that there are many more interbreedings of animals and humans, perhaps more than at any time in our history. And that will increase as temperatures continue to rise.
The scientists also found that heat waves attract more people to water-related activities. This increases the risk of waterborne diseases like gastroenteritis, which causes diarrhea and vomiting. It’s often caused by bacteria or viruses in the water, including the well-known norovirus, or winter vomit, which is somewhat misleading as it can also occur in summer.
They also chronicled how storms and floods forced people to move. People bring diseases like Lassa fever, cholera and typhoid with them. These infectious diseases can be prevented with vaccines or treated with antibiotics, but they can still cause many illnesses and be dangerous to those at risk.
Finally, the scientists reported an increase and worsening of asthma symptoms. This could be due to increasing pollution levels, but was most likely also due to an increase in allergens released by plants and fungi. An asthma attack can be triggered by pollen or other plant products. An increase in temperature has been linked to greater release of pollen, which in turn increases asthma. Do you remember when the pollen count was announced on the radio? We may have to come back to that to warn people.
The authors of this important study conclude that there is no area of global health that is not affected by climate change. They also remind us of the economic cost of infectious diseases, mentioning that the Covid-19 pandemic has cost the US economy $16 trillion by some estimates.
It’s a very important study because it tells us that it’s not just rising sea levels or more storms that will harm us. There will also be a whole host of diseases. This gives our species, which is under siege by infectious agents, more incentive than if we need it, both for our health and for our economy. We must stop global warming as soon as possible.
Luke O’Neill is Professor of Biochemistry in the Department of Biochemistry and Immunology at Trinity College Dublin
https://www.independent.ie/opinion/comment/climate-crisis-is-creating-the-perfect-storm-for-infectious-diseases-41941754.html The climate crisis is creating the perfect infectious disease storm