At first glance, infectious diseases and global warming appear to have little in common. One is an existential threat to human civilisation, discovered recently but entirely in our hands to prevent, while the other has been a perpetual part of nature, and cannot, despite medicine’s best efforts, ever be fully eradicated. Yet the two are inextricably linked. Much has been written about how global warming will release diseases frozen in arctic permafrost; indeed, already some Siberian children have died of diseases that global warming awoke. But as interesting as these stories are, they are not the main reason why global warming threatens to make infectious disease run rampant. That honour falls to global warming expanding the range for the greatest killer in the history of humanity, the mosquito.
As many of half of all humans that have ever lived may have died of malaria, which is just one of, though admittedly the deadliest, of the diseases spread by mosquitos. Add to that dengue, yellow fever, chikungunya, and West Nile fever, amongst others, and it is clear that the mosquito is the greatest mass murderer in human history. The diseases spread by this insect have shaped the patterns of European colonisation in Africa and the Americas, have led to the collapse of armies, and have shaped the layout of cities from Nairobi to Bogota. Even in 2020, with the world being swept in the middle of the COVID-19 pandemic there were over 200 million cases of malaria.
Despite the long dominance of the mosquito and its diseases over human society, its role today is mainly forgotten. This is because, in much of the world, the mosquito and its diseases have been bested. Ever since Ronald Ross discovered that malaria was carried by the female mosquito, Carlos Finlay discovered that yellow fever was also carried by mosquitos, and William Gorgas discovered how to deal with both of them, we have been able to successfully carry out eradication programs in much of the world. So successful have these programs been that, in spite of the over 200 million cases of malaria in 2020, only 400,000 people died of it. 400,000 deaths of a preventable disease are of course 400,000 too many, but it is a major triumph of modern medicine that malaria has gone from the main killer of humans to a statistically insignificant one.
Sadly, it appears that this period of the last century, when humanity has had mastery over mosquito, may be a brief interlude between the more natural states of mosquito have dominion over humanity. This is not because our current treatments and preventions of malaria no longer work, but because the range of malaria bearing mosquitos is expanding at a rate faster than the rate at which we can build anti-malarial infrastructure. A recent study in Lancet Planetary Health suggested that, by 2070, 4.7 billion more people may be at risk to mosquito borne illnesses such as malaria than were in 1970. This is not just due to the mosquito’s spread north and south to newly sub-tropical zones, but also due to the heating up of many highlands across the tropics. This latter element is the greatest driver of increased risk, since over the century many major cities in the tropics, such as Nairobi, Bogota, and Mexico City, were built just above the malaria zone. These are all expected to fall into the malaria zone in the next century, and frankly lack the medical infrastructure to cope with diseases they were built to avoid. Already in East Africa we are seeing a rise of mosquito borne infectious diseases in urban centres leading to spikes in diseases long eradicated in the traditionally susceptible lowlands. Add to this the hectic space of population growth in these cities, with people often left to live in unplanned and unsanitary slums, and we have a recipe for plagues of malaria and dengue that would have been familiar to a 19th century novelist.
As terrifying as the prospect of new pandemics of old mosquito borne illnesses are, we as a society can prevent it. It will however require the sort of long-term planning and concern for the world’s poorest that capitalism severely discourages. Malaria, and this cannot be stressed enough, is an entirely preventable illness. The only reason why it has not been eradicated so far is because its current victims are amongst the poorest people on earth, and there is no profit motive for saving those who cannot pay. If wealthy nations were to pay for anti-malarial treatments and preventative measures like malaria nets to become abundant in the poorest areas of the new malarial zone, there is no need for a second coming of this old pestilence. Indeed, in those wealthy countries where malaria and other mosquito borne illnesses are predicted to re-emerge, such as Greece and Italy, I suspect that these measures will be enacted. But we as socialists and internationalists have to ensure that we extend these protections to all of our fellow humans, no matter how poor they may be.