People & Culture

Ebola’s evolving geography: Why this year’s outbreak has spread further than ever before

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There has never been a confirmed case of the Ebola virus in Ghana, but the fear that there will be soon is palpable in the streets Accra, its modern capital city. A taxi’s radio crackles out the text of a World Health Organization fact sheet on the disease verbatim. Hawkers wading into stopped traffic holding newspapers with the headline “Ebola Scare.”

That headline was a false alarm, but the fear is not unjustified. An American who died in a local hospital turned out to have been infected by another hemorrhagic fever, but given the breadth of the 2014 Ebola outbreak, it could just as easily have been the first confirmed case of the dreaded disease in this West African country.

The scare pressed home an essential point — human geography is a key component of epidemiology. The ways in which people move and interact with each other are critical in determining just how fast and how far an infectious disease can spread.

Before it finds a human to host it, the Ebola virus is found in a reservoir animal, often the fruit bat. These ubiquitous bats eat fruit hanging high up in trees, dropping partially consumed fruit to the ground. There, other animals such as monkeys, antelope and porcupines eat the leftovers and contract Ebola from remnant bat saliva on the food. In West Africa, all of these animals — even the fruit bat — are served up on local plates. The consumption of this bush meat — and the bodily fluids it contains — often accounts for the virus’ initial transmission to humans, though this can also occur through the handling of dead animals by farmers and hunters.

Once transmitted via animal fluids, Ebola’s transmission between humans is similarly fluid driven. As viruses go, it is not highly contagious. In fact, prior to this year there were less than 2,000 recorded cases since its identification in the late 1970s, and unlike many viruses, Ebola is at its most contagious when it is obvious — when the infected person is extremely ill. The disease causes vomiting and diarrhea, and both fluids are rife with the pathogens by which the virus spreads.

This begs the question: why has the total number of recorded cases almost doubled since the beginning of the current outbreak in February 2014? The answer is a combination of virology and geography.

Across West Africa, communal taxis and minibuses are the main form of transportation. Every day, millions of people are jammed shoulder to shoulder into Nissans and Toyotas that nimbly pick their way through traffic along frenetic urban thoroughfares and bump their way along dusty back roads. On one of these crowded minibuses, 2014’s unprecedented Ebola outbreak began its spread. A woman fell ill at a market in Guinea, and was cared for by her sister. Her sister then crammed into a crowded communal taxi to Monrovia, the capital of neighbouring Liberia.

In the process, five people pressed against her in the taxi were infected, and then released into a crowded city that counts more than 400,000 residents. She then got a ride from a motorcyclist to the rubber plantation where her husband was employed. The motorcyclist may have been infected as well, and it’s unknown where he may have gone with the virus, or who he might have infected.

One reason the 2014 outbreak of Ebola is so much bigger than previous outbreaks is that people moving around West Africa have brought the disease into more densely populated areas than ever before. It’s even been confirmed in the Nigerian capital of Lagos, a mega-city with a population nearing 20 million.

Borders are open between West African countries due to a regional passport agreement, and despite there being no cases of the disease in Ghana, everyone is on high alert. Freedom of movement for individuals means freedom of movement for the diseases they carry.

In an attempt to stem Ebola’s spread, Ghana recently cancelled international flights from all countries with confirmed cases. Yet Ebola can incubate for 21 days in an infected person without symptoms revealing themselves. Given that a large group of individuals from West Africa and points beyond regularly move around the region for business and work, the ban may not be enough, given the uniqueness of the outbreak of 2014.

It has killed more people than any previous outbreak of the disease, but — counter-intuitively — its death rate has been relatively low. At 55 per cent, it is incredibly high among infectious diseases generally, but in its most virulent outbreaks, Ebola has killed upwards of 90 per cent of those infected. (The lower death rate in this case could be partly attributable to a measure of success achieved in treating the disease)

A lower mortality rate can also hasten the spread of the virus. Since the virus’ host is alive longer, there is a greater period in which it can be transmitted. The infected can travel further and interact with more people, and every time bodily fluids are exchanged — in sweat or sperm or saliva or otherwise – there is a chance for the disease to be transmitted. Sex, kissing, breast feeding and caring for the sick are all activities with some risk.

A further concern in the disease’s spread is the possibility of its sexually transmissibility by surviving men. The Ebola virus has been observed to stay alive in sperm for as long as two months after infection. A similar virus known as the Marburg virus has been confirmed to have been sexually transmitted, but Ebola itself has not yet been known to be a sexually transmitted infection. Doctors nevertheless strongly encourage condom use in surviving men.

For Ghana, as elsewhere in West Africa and perhaps even beyond, the key to controlling the virus in its current incarnation lies in education. Whether that means encouraging condom use in survivors or the Howie Mandel-popularized germ proof fist bump, raising awareness of the role of fluids and bodily contact in Ebola’s spread will be key to containing an outbreak of the virus that has already been deadlier than all that came before it.

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