One of the most frightening mysteries of Africa's latest Ebola outbreak is how the virus seems to have jumped from its traditional home in Central Africa to an entirely new region in West Africa, nearly 2,000 kilometres away.
The answer may give significant clues to environmental and economic trends in Africa, where dramatic changes – including massive deforestation – have been accelerating in recent years with little attention paid to the consequences.
The Zaire strain of Ebola is one of the world's deadliest viruses, with no known cure and a 90-per-cent fatality rate. Its victims can die within days from severe bleeding. In the latest outbreak, 134 suspected cases of Ebola have been reported in Guinea so far, and the death toll from these cases has now climbed to 84.
Suspected cases have also been reported in Liberia, Mali and Sierra Leone, and two deaths from Ebola have been confirmed in Liberia. One of the suspected cases involved a Liberian hunter who apparently caught the virus after eating a fruit bat. He reportedly died within 30 minutes of arriving at a hospital.
Health agencies have been scrambling to help the victims, while doctors and nurses are protecting themselves with elaborate uniforms, masks and goggles.
Many people in the three affected countries have begun wearing gloves and avoiding handshakes. Liberia's health minister has even gone so far as to urge people to stop kissing or having sex.
This is the first outbreak of Ebola in the West African countries. It's theoretically possible that the virus had been lurking for decades in natural reservoirs in the animal population of southern Guinea, where the jungle environment is similar to Central Africa. But if so, why did it never cause an outbreak until now?
It seems more likely that the Ebola virus travelled from its normal home in Central Africa – but this raises the key question of how the virus managed to migrate across so many hundreds of kilometres.
One possible explanation is deforestation. Anyone who has travelled in Africa in recent years has witnessed the phenomenon: new logging roads, the massive charcoal industry, slash-and-burn farming, the booming Chinese demand for African timber, and huge mining concessions that require forests to be chopped down.
Scientists have already established a link between deforestation and other diseases such as malaria. Deforestation tends to reduce biodiversity, create new breeding habitats for malaria-carrying mosquitoes and increase the contact between humans and mosquitoes at the edges of these newly fragmented forests. But can it also be linked to the spread of Ebola?
There are two ways in which deforestation could contribute to Ebola. First, it could accelerate the animal-migration trends that spread the Ebola virus. The virus is believed to be linked to certain species of forest-dwelling fruit bats, which are considered a delicacy in some parts of West and Central Africa. The bats could be spreading the virus directly to humans who consume them. Moreover, the fruit infected by these bats can drop to the ground and be consumed by chimpanzees, gorillas and other primates, which can then spread the virus to humans through the bush-meat trade – a common source of food in impoverished African countries.
Analysts suggest that the fruit bats of Central Africa, pushed out of their home territories by logging and deforestation, could have migrated to similar forests in West Africa and mingled with the bat population there, causing the virus to spread.
Deforestation also makes it much easier for the bush-meat industry to thrive. New roads and cleared forests lead to more contact between hunters and wildlife. Deforestation encourages people to move into new areas of the bush, where they can more easily hunt bats and primates such as chimpanzees and monkeys – the intermediaries in spreading the Ebola virus from bats to humans.
In the wake of the latest Ebola outbreak, the government of Guinea has advised people to stop consuming the meat of chimpanzees, monkeys and bats. But this is a stopgap measure in a region where bush-meat is a long-entrenched source of food.
With help from the World Health Organization and independent aid groups such as Médecins sans Frontières, the Ebola outbreak in Guinea is likely to be contained. But the outbreak is a warning sign. It shows how Africa's rapidly changing economy – and its dramatic environmental disturbances – can have unintended consequences for the people of the region.
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Geoffrey York