Is Climate Change Contagious?
As the conditions we live in change with global warming, infectious diseases all over the globe are on the move.
Following the controversial outcome of this year’s COP27 summit, the topic of climate change has once again claimed the attention of world politics. And rightly so – as the planet warms, sea levels are rising, farming seasons are disrupted and our global ecosystem is going extinct at an unprecedented rate.
On top of this, we face another problem: infectious disease. Climate change now poses a direct threat to our health, as an intensifying greenhouse effect and changing weather conditions perpetuate the spread of new and existing diseases through our food, water, and the animals around us.
How is this happening?
In epidemiology, a disease vector is an organism that transmits an infectious pathogen to another organism. Take Aedes aegypti, the yellow fever mosquito, or the Ornithodoros tick responsible for transmitting African swine fever. As ectotherms, neither organism is capable of regulating their own body temperature, thereby restricting their range of habitation to tropical climates. As the earth warms, however, these animals are given an ever-expanding geographical range in which to thrive.
With rising temperatures and increasing precipitation levels (e.g., rainfall), these animals are also given increasingly favourable environments in which to reproduce. Why? Since vectors are ectothermic, they are highly dependent on the warmth of their surroundings to remain active. This same concept also applies to the pathogen within. Plasmodium, the causative agent of malaria, matures and travels through its mosquito host much faster with just a minute increase in temperature. As a result, a 2014 study looking at malaria transmission in Western Kenya found that a 0.5°C increase in temperature caused an eightfold increase in malaria cases.
Extreme weather may only exacerbate the issue
As the climate warms, we are seeing a shift toward more frequent extreme weather events. Storms, floods and heavy rainfall each leave behind pools of stagnant water that serve as the ideal breeding ground for mosquitoes, alongside the many infectious microbes they spread. Drought too may contribute to this, as flowing waterways dry up and come to a halt. These events are often accompanied by the breakdown of normal hygiene practices too, as areas affected struggle to recover. As warming climates see an increase in precipitation, then, we can expect to see a global increase in the abundance of infectious mosquitoes spread over expanded geographical ranges; a trend mirrored in diseases spread through contaminated food and water.
While there are a multitude of ways in which water and food may be contaminated, including the improper storage of sewage alongside chemical, and faecal waste, the largest threat water and food supplies face with climate change is the resulting effect on precipitation. As warming climates contribute to an intensified water cycle, ill equipped water treatment plants, sewage infrastructures, and sanitation structures across the globe are being overwhelmed. This is especially problematic in LEDC countries such as Uganda, Chad, and Ethiopia, where this leads to the contamination of public water sources. Moreover, pathogens found in faecal matter are more likely to enter surface waters due to the sheer intensity of resulting surface runoff.
What can we do to stop this?
We have all heard the phrase “reduce, reuse, recycle”, or how we need to abolish single use plastic, but these solutions fail to offer protection in the face of an already emerging problem. In recent years, several technological solutions have been offered, including the release of genetically modified mosquitoes designed to reduce the population of animals able to spread disease. In reality, however, as highlighted in the recent COP27 summit, significant funding and international cooperation is now required to help developing nations prepare for a resurgence of contagious disease in the face of inevitable climate change.