Dr. David Blackley, alumnus of the ETSU College of Public Health and epidemiologist for the National Institute of Occupational Health and Safety (NIOSH), is a lead author of an article in Science Advances. The article, “Reduced evolutionary rate in reemerged Ebola virus transmission chains” identifies Ebola virus disease clusters that likely arose from persistently infected sources, highlighting the risk of Ebola flare-ups even after the outbreak has been declared over by the authorities.
[Photo: Dr. David Blackley]
After two years of dealing with the Ebola virus disease, all chains of human-to-human transmission of the virus have finally stopped in Western Africa. The region remains under enhanced surveillance to rapidly detect any cases associated with a missed transmission chain or a reintroduction of the disease. Since Ebola transmission apparently ended in Liberia, the country has experienced several renewed outbreaks. Dr. Blackley and the research team examined a “flare-up” in June 2015 that resulted in seven confirmed cases.
On June 28, 2015, an oral swab was collected from a deceased 17-year old male in the village of Needowein in Margibi County. The sample tested positive for the Ebola virus disease and from June 30 to July 12, six additional epidemiologically linked individuals tested positive for Ebola. Interviews with patients and their families, friends and contacts indicated no recent activities such as travel to neighboring countries, hosting of visitors, funeral attendance, sexual contact with Ebola survivors, and/or consumption of infected animals.
Comparison with other Ebola virus sequences from Western Africa indicated that the Needowein flare-up was a continuation of the Western African Ebola virus disease outbreak that began in 2013 and was not caused by an independent introduction from an unknown nonhuman reservoir. The authors state, “Given the ongoing surveillance in Liberia during this period and the absence of an Ebola virus disease case in Liberia for three months before this flare-up, research indicates that the Needowein flare-up originated from a persistently infected source.”
The investigators’ goal of interrupting transmission and preventing further spread of the virus was accomplished, and on September 3, 2015, Liberia was again declared free of Ebola. A reemergence of the disease during November, 2015 lead the team of investigators to speculate that the new cluster is also linked to the previous transmission chain. They conclude Liberia, Sierra Leone, and Guinea will need to “maintain heightened vigilance during the coming months, or perhaps longer, to rapidly contain any future flare-ups.”
Dr. David Blackley received a Doctor of Public Health degree from East Tennessee State University in May 2013. He then began a two-year postdoctoral fellowship with the Epidemic Intelligence Service of the Centers for Disease Control and Prevention (CDC) in Atlanta. He now serves as a research epidemiologist in the Surveillance Branch, Respiratory Health Division of NIOSH.