As social scientists studied communities affected by the slew of outbreaks that swept through Central Africa in the 1990s and 2000s, virologists began to wonder if the unprecedented number of cases were somehow connected. Initially they developed a theory that a single Ebola outbreak from a single index case was slowly simmering and spreading through Zaire (and then DRC), Gabon, Congo, CAR, Sudan, and Uganda. The reality that the outbreaks included several species of the virus and a multiple suspected index cases connected mostly to the handling of animal carcasses squashed the theory of a single outbreak, but still the question remained, why this sudden and prolonged string of separate and distinct outbreaks?

Scientists next looked for larger environmental patterns that might connect the Central African cases. Most outbreaks of Ebola occur in between the dry and wet seasons, but there has been speculation that broader climatic event might be connected to the sustained spike in cases. The 1976 simultaneous outbreaks of separate species only a few hundred miles from each other also points to an environmental occurrence activating the virus and allowing it to jump from the reservoir to monkeys and humans. Scientists have been studying satellite photographs of the Congo Basin from the past few decades in an attempt to detect any environmental changes that overlap spatially with flare ups of Ebola. These studies have found that especially arid dry seasons disrupt the ecosystem in the jungle, leading animals to move beyond their normal confines in search of food and water, which results in increased human-animal contact.[1] If this is accurate, global warming has serious implications for Ebola outbreaks.

Another study that may lend further support to the environmental activation hypothesis was conducted in 2010 when scientists examined the genomes of living African bats and rodents and found ancient “fragments” of filoviruses in their genomes. Through recent advances in the fascinating subfield of paleovirology the researchers were able to estimate that filoviruses are likely tens of millions of years old based on the genetic remnants of the disease shared by the mammals coupled with the scientists’ knowledge of the mammals’ shared evolutionary trees. If rodents and bats have carried filoviruses for tens of millions of years as they migrated across the world, it’s no surprise that strains of Ebola exist in both Sub-Saharan Africa and the Philippines. The study goes on to suggest that other rodents, marsupials, and bats may carry yet unknown forms of filoviruses in the Americas.[2] The fact that we’ve only seen the virus pass from reservoir to human in Central Africa and the Philippines, lends credence to the idea that it is something particular to the Central African environment (that the Philippines may share) that is “activating” or allowing the virus to jump from the reservoir to larger mammals. Could global warming activate latent filoviruses in other regions of world? [Or, alternatively perhaps other New World strains are similar to the Reston species in that they don’t cause human illness when spread to humans and therefore haven’t been detected yet.]

As promising as the research has been into detecting an environmental link, in focusing on identifying climatic trends connecting the past twenty years of outbreaks, scientists have neglected to consider the often-horrific human history of Central Africa as a potential source of explanation for the string of outbreaks. In the aftermath of the Rwandan civil war and 1994 genocide, the deadliest conflict since World War II unfolded across Central Africa, killing over four million people, displacing many millions more, and dragging in soldiers from throughout the region. The First and Second Congo Wars have not received nearly as much scholarly attention as they require, but books such as Africa’s World War written by Gerard Prunier begin to document the devastating bloodbath that occurred as troops from Rwanda and Uganda marched across lawless Zaire to evict Mobutu from his rotting seat of power in Kinshasa. Two decades later, the conflict continues to this day with fighting between Kagame’s Rwanda and rebel groups such as M23 in eastern DRC. Additionally South Sudan has suffered its own bloody history that persists despite independence from northern Sudan, and the Lord’s Resistance Army has terrorized Northern Uganda/CAR for many years, displacing numerous people.

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Charcoal mural in an IDP camp near Gulu, Uganda (Mark Duerksen, 2009)

The result of the countless armed conflicts in Central Africa has been an upheaval of societies across region, causing an increased likelihood of human exposure to Ebola as starving refugees and soldiers turned to bush meat while they roamed through the Congo’s dense forests, and as they displaced animals by burning and logging forests, which may have put primates in greater contact with both humans and the reservoir. It would be interesting to see what further spatial research tracing the conflict and the virus over the past 20 years might reveal.

Scientists’ omission of the deadliest conflict since WWII from their causal considerations and the dismal results of the ethics review of Ebola research (previous post) suggests a troubling trend where scientists studying Ebola in reality know very little about the region and the people affected by the virus.

[1] Stephen Pincock, “Seeing Ebola from Space,” The Scientist, May 1, 2006. Available online: http://www.the-scientist.com/?articles.view/articleNo/23952/title/Seeing-Ebola-from-space/

[2] Derek J Taylor, et al., “Filoviruses are ancient and integrated into mammalian genomes,” BMC Evolutionary Biology, 10(2010), 1471-2148.

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