Disease epidemics are as much markers of modern civilization as they are threats to it. What successfully evolves and spreads depends on the matrix of barriers and opportunities that a given society presents to its circulating pathogens. For most of its history, for example, Vibrio cholerae lived off plankton in the Ganges delta. It was only after significant layers of the population had switched to an urban, sedentary lifestyle, and later had become increasingly integrated by nineteenth-century trade and transport systems, that the cholera bacterium evolved an explosive, human-specific ecotype. Simian immunodeficiency viruses emerged out of their non-human Catarrhini reservoirs in the form of hiv when colonial expropriation turned subsistence bushmeat and the urban sex trade into commodities on an industrial scale. Domesticated livestock has supplied a source for human diphtheria, influenza, measles, mumps, plague, pertussis, rotavirus A, tuberculosis, sleeping sickness and visceral leishmaniasis. Ecological changes wrought upon landscapes by human intervention have facilitated spillovers of malaria from birds, and of dengue and yellow fever from wild primates. The new pathogens adapted to improvements in medical technologies and public health, while innovations in agricultural and industrial methods accelerated demographic shifts and new settlement, concentrating potential host populations and thereby promoting new rounds of spillover.
Policies aimed at re-engineering local economics for the benefit of multinationals have had a drastic impact on landscapes and ecosystems, and thus upon the fortunes of infectious disease. As epidemiological history attests, context is more than just a stage upon which pathogens and immunity clash. The regional agro-economic impacts of global neoliberalism can be felt across the levels of biocultural organization, down as far as the virion and molecule. The exploration of such connections may well be a cutting-edge question for the twenty-first century. A growing public- and animal-health literature suggests that current patterns of agro-economic exploitation raise the risk of a new pandemic, whether triggered by an rna virus like Ebola or sars, or by some other pathogen. Ecosystems in which ‘wild’ viruses are controlled by the rough-and-tumble of environmental stochasticity are being drastically streamlined by deforestation and plantation monoculture. Pathogen spillovers that once died out relatively quickly are now discovering chains of vulnerability, creating outbreaks of greater extent, duration and momentum. There is a possibility that some of these outbreaks may come to match the scale of 1918’s influenza pandemic, with a global reach and high rates of incapacitation and mortality.
Capitalist agri-business is increasingly transforming Planet Earth into Planet Farm. Forty per cent of the world’s land surface is now dedicated to agriculture, with many millions more hectares set to be brought into production by 2050. Livestock, representing 72 per cent of global animal biomass, is simultaneously highly concentrated and widely dispersed across the planet’s surface. The livestock sector uses a third of available freshwater and a third of cropland for feed. By its global expansion, commodity agriculture acts as a nexus through which pathogens of diverse origins migrate from even the most isolated reservoirs in the wild to the most globalized of population centres. The longer the associated supply chains and the greater the extent of deforestation, the more diverse (and exotic) the zoonotic pathogens that enter the food chain. Among such emergent pathogens are industrial Campylobacter, Nipah virus, Q fever, hepatitis E, Salmonella enteritidis, foot-and-mouth disease and a variety of novel influenza variants.footnote1 Intensive agriculture’s diseconomies of scale extend beyond the unintended epidemiological consequences of globalizing transport and distribution. Its production cycles degrade the resilience of ecosystems to disease, and accelerate pathogen spread and evolution by giving rise to genetic monocultures, high population densities and expanding exports. In this essay, we describe the emergence of an urbanized Ebola in West Africa in late 2013 as a quintessential example of such a transition.footnote2
The outbreak of Zaire ebolavirus (zebov) in West Africa, the largest and most extensive yet recorded, began in forest villages across four districts in southeastern Guinea in December 2013. The epidemic subsequently spread across Guinea, Liberia and Sierra Leone—including the capital cities Conakry and Monrovia—before infiltrating Nigeria and Senegal. The World Health Organization declared the outbreak to be a Public Health Emergency of International Concern. By the end of 2015, 28,000 cases of infection and 11,000 deaths had been recorded. Many of the thousands who survived infection suffer long-term effects such as eye disease, hearing loss, arthralgia, anorexia, difficulty sleeping and ptsd.footnote3 The earliest documented cases of the outbreak in West Africa seem to be those of two young village children, a 2-year-old brother and 3-year-old sister, north of Guéckédou, a Guinean town with a population of 200,000. One group of researchers have suggested that the initial zebov spillover occurred when children outside the Guinean village of Meliandou caught and played with bats from an insectivore species (Mops condylurus) previously identified as an Ebola carrier.footnote4
But the focus on an index-case ‘patient zero’ could be misplaced: Ebola may have been circulating in the region for years.footnote5 Studies found antibodies to multiple species of Ebola, particularly the Zaire strain, in patients in Sierra Leone several years earlier, while phylogenetic analyses of the virus’s own genome date the lower bound of zebov’s entry into West Africa back to a decade ago.footnote6 Our own research group proposed that this strain arose as the production of oil palm, to which Ebola-bearing fruit bats are attracted, underwent a classic process of consolidation, enclosure and proletarianization in Forested Guinea.footnote7 The transformation in agro-forestry curtailed artisanal production and may have expanded the human-bat interface over which the virus crosses.