Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science Volume 12, Number 4, 2014 ª Mary Ann Liebert, Inc. DOI: 10.1089/bsp.2014.1563
Medicine for Policymakers
Medicine for Policymakers is a Journal column that provides decision makers with brief explanations of the meaning and implications for biosecurity of clinical issues. The articles describe, for a nonmedical audience, hospital practices, medical challenges, healthcare delivery issues, and other topics of current interest. Readers may submit ideas to the column’s editor, Amesh A. Adalja, MD, through the Journal’s editorial office at [email protected]
Ebola in West Africa: A Familiar Pattern? Amesh A. Adalja
he current outbreak of Ebola in West Africa—a region that has been largely devoid of visitations from this virus—has sparked many news stories and fueled speculation about how such outbreaks are started, sustained, and eventually controlled.1 However, with some important caveats, this outbreak displays many of the characteristics of prior outbreaks, the first of which occurred in 1976.2
Spillover from Animal Reservoir Ebola virus disease (EVD) occurs after infection by 1 of the strains of the Ebola virus. Thus far, 5 strains of the virus have been identified: Zaire, Sudan, Tai Forest, Bundibugyo, and Reston (the subject of Richard Preston’s The Hot Zone). Of the 5, only the Reston strain does not cause disease in humans. Each strain has a different mortality rate, with Zaire being the most lethal with a 90% rate. Because of its high mortality rate, it has been pursued as a bioweapon, and that is reflected in its designation as a category A agent and the requirement that laboratory work with it be conducted in a the highest level of containment, BSL-4.2 When Ebola appears it often follows a specific pattern: a sick individual (the index patient) travels to a village health facility, he or she is seen by medical practitioners, and an outbreak begins. The illness in the index patient is often shrouded in mystery and presumably arises after contact
with some of Ebola’s reservoir species, such as other primates or antelopes. Contact with bats, the ultimate source of Ebola, may also have occurred.
Severe Symptoms, Inadequate Infection Control The symptoms of EVD include fevers, chills, muscle pain, and rash. The disease can progress to a state in which the individual is in shock with an inability to maintain an adequate blood pressure, and the blood may lose the ability to clot, leading to the hemorrhagic manifestations and rapid death with which the virus is highly associated.2 Once in the village setting, the virus often finds ample opportunity to spread via ineffective or nonexistent infection control practices in healthcare facilities. As Ebola’s mechanism of human-to-human spread is exclusively related to contact with blood and other bodily fluids, it is orders of magnitude lower in contagiousness than viruses such as measles or influenza. This is why local healthcare workers, who are most likely to be exposed to bodily fluids, are often over-represented in the tallies of those afflicted with EVD. An additional factor in Ebola’s spread is in the funeral practices surrounding fatal cases in which contact with the corpse and its bodily fluids occurs.2
Amesh A. Adalja, MD, is a Senior Associate, UPMC Center for Health Security, Baltimore, Maryland. 161
EBOLA IN WEST AFRICA
Since there is no antiviral agent that is effective against Ebola and no vaccine to prevent it—though several are in development—the chief means to extinguish an Ebola outbreak is to initiate simple hygienic infection control procedures in affected locales. Donning gloves, gowns, and eye protection while caring for patients, along with the proper precautions during funeral procedures, is usually all that is required to stop the virus from spreading. The fact that Ebola kills fast and at a high rate provides the virus with little opportunity to spread, thereby making an outbreak almost self-extinguishing as hosts for the virus become scarce.2
West Africa Outbreak Larger and Unusual The start of the West African outbreak, with cases initially centered in Guinea, began in a familiar way, but very soon cases were seen in other locations such as Liberia and Sierra Leone. The outbreak has continued to smolder longer than anticipated, even after infection control has been instituted. Currently, more than 500 cases have been reported. As of this writing, questions arise about this outbreak, including:
Is spread occurring because of continued lapses in infection control? Is behavior change with funeral practices sufficient?
How significant is the relative inexperience of West Africans in dealing with Ebola? Is there ongoing spillover from reservoir species (eg, bat soup consumption)? For an outbreak of any pathogen to be controlled, understanding the dynamics of transmission events is crucial to tailoring an efficacious response.
References 1. Ebola virus disease (EVD). World Health Organization website. http://www.who.int/csr/disease/ebola/en/. Accessed June 10, 2014. 2. Peters CJ. Marburg and Ebola viral hemorrhagic fevers. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, PA: Churchill Livingstone; 2010. Address correspondence to: Amesh A. Adalja, MD Senior Associate UPMC Center for Health Security 621 East Pratt St., Ste. 210 Baltimore, MD 21202 Email: [email protected]
Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science