By Neal Lineback, Baker Perry and Mandy Lineback Gritzner, Geography in the NewsTM
Ebola Virus Spreads to West Africa
Dangerous viral hemorrhagic diseases, particularly including the deadly Ebola, are emerging as threats to humans around the world.
The deadly disease Ebola has been the focus of intense news coverage since the publication of the book, The Coming Plague: Newly Emerging Diseases in a World Out of Balance (Penguin, 1995) by Laurie Garrett, aroused public interest in the threat of new infectious diseases.
A recent outbreak of Ebola in West Africa has medical personnel scrambling, as it has spread into Guinea, then into Liberia and Sierra Leone, according to news reports. It has now entered Guinea’s capital city of Conakry’s densely packed urban population of more than two million. At last reports, over 240 people had contracted the disease and it had killed more than 140 people. Suspicions are that the ebolavirus may have arrived in a fruit bat whose flesh might have come in contact with a human, although the source is still unsubstantiated.
Understanding the spatial distribution of disease is a critical component of public health. An example is the well-known case of Dr. John Snow, who mapped cholera deaths in London in 1854, establishing a relationship between contaminated water and cholera. This study demonstrated the importance of the spatial perspective in the study of disease.
Medical geography, as this specialization is termed, is crucial in understanding linkages and spatial patterns associated with the emergence of new infectious diseases on both a local and global scale. Finding the geographic origin of a disease is often critical in determining its ecology, its vector(s) and its spatial diffusion, all of which are important to its containment and treatment.
Viral hemorrhagic fevers are perhaps the most feared and least understood of the emerging infectious diseases. Hemorrhagic fevers are divided into four main families: arenavirus, bunyaviridae, filovirus and flavivirus. Their symptoms consistently begin in humans as a headache, acute infection and fever, progressing to increased leakage of blood and fluids within the body. Finally, the progression of the disease leads to tissue degeneration and massive hemorrhaging from body orifices, most often leading to death.
Species of undomesticated (wild) animals are the primary reservoirs for most or all of the hemorrhagic viruses. Sometimes intermediate vectors, such mosquitos, fleas or ticks, may transmit the virus to humans. Transmission also may occur, however, through human contact with the raw flesh or body fluids of infected animals or humans, creating exceptional difficulties for family members and health workers who have to live with or deal with an infected person.
Among the viral hemorrhagic fevers, the filoviruses have aroused the most interest and concern. Since the discovery of Marburg virus in a German monkey house in 1967, officials have documented numerous outbreaks of Marburg and its close relative Ebola.
Mortality rates for Marburg and Ebola viruses are astoundingly high at 70 percent. In the past, Marburg outbreaks have occurred in Germany, Zimbabwe and Kenya. In recent years, however, outbreaks of Ebola have been more prevalent than close relative Marburg, but these viruses are unpredictable.
The Centers of Disease Control (CDC) further divide Ebola into at least four “subtypes,” based upon their geographies: Zaire, Sudan, Tai Forest (Ivory Coast) and Bundibugyo (Uganda) ebolaviruses (all of which may have somewhat different genetic compositions). Of the four, Ebola Zaire is reported as the most lethal, ultimately killing 83 percent of those infected during the outbreaks of 1976 and 1995 in Zaire. The current outbreak in West Africa may actually be a variant of the Zaire ebolavirus, rather than the region’s previously recognized nearby Tai Forest ebolavirus, according to the CDC.
All of the Ebola subtypes are found in the rain forest regions of Central and West Africa. An errant outbreak called here the Reston ebolavirus event appeared in a monkey house near Reston, Va., in 1989. This outbreak created much alarm and apprehension among the research and public health community. Although this particular subtype killed 85 percent of the monkeys infected, none of the four infected people died and the event was contained and eliminated.
Though most hemorrhagic viruses are sources of concern, it is equally important to recognize that they are not all relegated to the rain forests of Africa, but are indeed present in many countries of South America and even in the United States. But most of these are not as deadly as Ebola.
Excluding Ebola for the moment, the twenty-one year period since 1993 has witnessed numerous outbreaks of other viral hemorrhagic fevers, including some caused by totally new or previously unrecognized viruses. The hantavirus outbreaks in California, New Mexico and South America were traced to fleas from rodents, as was Bolivian hemorrhagic fever. Rift Valley fever and Crimean-Congo hemorrhagic fever outbreaks in Egypt and the United Arab Emirates apparently were linked to blood-sucking insects, probably mosquitoes and ticks.
Of all of the hemorrhagic fevers, however, Ebola is the most feared. Health researchers all over the world are working hard to trace the origins of this virus wherever outbreaks occur. It is extremely dangerous to residents and travelers alike, once it enters a population.
The West African outbreak raises a new series of questions. How can Ebola be contained after it arrives in densely populated urban areas, particularly in poor countries? What species other than monkeys and bats might be reservoirs for Ebola in any particular outbreak? How can it spread in its natural environment from species to species? Can insects spread the virus? How can the local population avoid contracting the disease in its early stages? The West African outbreak is providing a new, if extremely dangerous, laboratory for researchers.
As societies and places become more closely linked through globalization processes, these newly emerging viral hemorrhagic fevers may pose an even greater threat to humans worldwide. Being aware of the threat can go a long way in containment of viral outbreaks, as people take precautions to avoid behaviors that spread the disease.
And that is Geography in the News.
Source: GITN 405, “The Deadly Ebola Virus,” May 13, 1997.
Co-authors are Neal Lineback, Appalachian State University Professor Emeritus of Geography, and Geographer Mandy Lineback Gritzner. Dr. Baker Perry of Appalachian State assisted in writing this article. University News Director Jane Nicholson serves as technical editor. Geography in the NewsTM is solely owned and operated by Neal Lineback for the purpose of providing geographic education to readers worldwide.