In 2014, the Ebola virus gained notoriety for the lives it took in such a short amount of time. While the panic surrounding the virus has since died down, Ebola continues to wreak havoc in West Africa. To properly contextualize the implications of this epidemic, it is important to understand the basics of how Ebola works—how the virus itself functions, how it spreads, and how it affects the human body.
The Ebola virus is classified in the order Mononegavirales, which includes the mumps, measles, and rabies viruses.1 There are currently five species of Ebola viruses: Zaire, Bundlibugyo, Sudan, Reston, and Tai Forest. The most lethal of these species, Zaire, is responsible for the 2014 outbreak. Ebola carries a negative-sense RNA genome that works by encoding mRNA (a type of RNA called messenger RNA) in the host cell.2 The mRNA strand is translated into seven viral proteins that allow replication of the Ebola virus. Newly formed Ebola virus buds out of the cell, and once the cell dies, it lyses, or bursts, releasing viral RNA to other cells within the body.
Ebola, like the swine flu, was likely first introduced into the human population through close contact with the bodily fluid of infected animals such as chimpanzees, gorillas, monkeys, porcupines, or fruit bats, which are the virus’ natural hosts.1 Although the virus is highly transmittable through bodily fluid, it is not an airborne disease; instead, the virus is transmitted only through direct contact of broken skin or mucous membranes with the bodily fluids of infected organisms and through direct contact with materials contaminated with these fluids.1 People are not infectious until they develop symptoms; however, they remain infectious as long as their bodily fluids contain the virus. For example, the Ebola virus can persist in semen for up to three months subsequent to recovery. The incubation period, or time interval from infection to onset of symptoms, is 2 to 21 days.1 The delayed onset of symptoms means that the infected individual may be unaware that he or she is carrying the disease.
During the 2014 outbreak, poor infrastructure, unsafe practices in burial ceremonies, and close contact between health-care workers and patients facilitated the spread of the virus.1 In West Africa, improperly disposed bodily fluids contaminated materials such as clothing led to infection of healthy individuals. Burial ceremonies themselves have contributed to the transmission of Ebola in West Africa; mourners who came into direct contact with the bodies of deceased individuals contracted the disease.1 In the U.S., the transmission of Ebola from patient Thomas Eric Duncan to nurses Nina Pham and Amber Vinson was likely caused by a breach in safety protocol; while healthcare workers are typically obligated to wear full body suits, any error in wearing or removing the suit could have exposed the nurses to Duncan’s bodily fluids.4
Ebola’s initial symptoms include the sudden onset of fever, fatigue, muscle pain, headache, and sore throat. These initial symptoms can often be confused with those of the flu, but they are followed by more severe ones including vomiting, diarrhea, rashes, and internal and external bleeding. While this disease has a high mortality rate of 50%,1 its transmission is more indirect than that of more common viruses such as the flu. Because of the routes of Ebola transmission are so limited, especially in areas with developed infrastructure, the CDC and other health experts predict that an Ebola outbreak in the U.S. would be highly improbable.5 The events of 2014 serve as a reminder of the importance of adequate infrastructure and safety protocols in order to limit the spread of future viral epidemics.
References
- World Health Organization. http://www.who.int/mediacentre/factsheets/fs103/en/ (accessed Nov. 1, 2014).
- Feldmann, H. K. Arch. Virol. Suppl. 1993, 7, 81–100.
- Mucous membrane. http://www.britannica.com/EBchecked/topic/395887/mucous-membrane (accessed Nov. 1, 2014).
- Alexander, H. Second Texas nurse contracts Ebola after treating Thomas Eric Duncan. http://www.telegraph.co.uk/news/worldnews/ebola/11164105/Second-Texas-nurse-contracts-Ebola-after-treating-Thomas-Eric-Duncan.html (accessed Jan. 17, 2015).
- Ebola transmission. http://www.cdc.gov/vhf/ebola/transmission/index.html?s_cid=cs_3923 (accessed Jan. 17, 2015).