The recent outbreaks of Ebola in Africa have focused media attention on viruses and the science of epidemiology.
image courtesy of the CDC
Let’s take a look at some questions about the Ebola virus:
What is the Ebola virus and what is happening in Africa?
Ebola is a virus that is part of the Filovirus family which includes Ebola and Marburg viruses. The genus Ebolavirus consists of five distinct viral species:
- Zaire ebolavirus (EBOV)
- Bundibugyo ebolavirus (BDBV)
- Sudan ebolavirus (SUDV)
- Taï Forest ebolavirus (TAFV)
- Reston ebolavirus (RESTV)
The first four of these species are dangerous to humans and make up the most commonly found ebolarvirus infections that occur in African outbreaks. The first on the list, Zaire ebolavirus is the most commonly seen species infecting humans. With a mortality rate at 50% and often near 90%, it is clearly one of the deadliest of human diseases. This figure shows the mortality rates of the current outbreak in Africa over the past few months, the most deadly outbreak ever recorded. The current outbreak is centered in an area not previously hit by past outbreaks. This time the disease is found not only in rural but also urban areas.
Image from Forbes.com. Circles are countries. Size is number of disease cases. Color is virulence, the case fatality rate from 0% yellow to red 100%. ‘Guinea’ represents West Africa. (Data: WHO / CC BY: JV Chamary / Source: http://onforb.es/Y3YjoG)
How does the Ebola virus affect the human body?
Ebola Virus Disease is characterized by an initial set of influenza like symptoms or symptoms of other commonly found tropical fevers.
By Mikael Häggström [CC0], via Wikimedia Commons
The virus targets neutrophils thus evading the immune system and also endothelial cells that line blood vessels. Eventually, this leads to massive hemorrhaging, the characteristic and lethal obvious sign of the disease. Symptoms take about a week to manifest after infection and death follows a week or so later.
While many are working on possible cures, to date there is no viable vaccine for the Ebola virus. A few drugs may one day be available but anything at present is highly experimental if promising. The best current treatment for ebola infection is prevention as well as measures to prevent the spread of the virus. While ebola is easily transmitted from one person to another, humans are not the primary host of the virus.
How is the virus transmitted to humans?
The five viruses in the Ebola genus are found in animals, bats in particular. Humans rarely become infected directly from bats, rather other animals become infected first and then humans consume those animals to come into contact with the virus. Human consumption of animal meats like duiker (a small deer like animal) or monkeys leads to infection. In some cases it is suspected that the eating of fruit bats also may transmit the virus to humans.
Once a human is infected the virus can be transmitted to health care worker or family members caring for the sick patient. The blood and body fluids are highly contaminated. Preventative measures including full body protective equipment and careful handling of those who do not survive the illness are necessary but not always implemented. In regions lacking resources, failure to understand and follow these basic preventative measures allows the disease to spread in epidemic form. In some cases, full scale quarantine measures are introduced as the only means of slowing the spread to neighboring regions.
Additional Resources:
Contributed by Michael Troyan. Michael is a regular contributor to our site. He has spent 20 years teaching non-majors biology and microbiology and currently works as an online instructor at Penn State University. He can be reached at [email protected]
