Medical Research: What is the background for this study? What are the main findings?
Dr. Drake: Ebola virus disease is a deadly illness caused by infection with the zoonotic Ebola virus. The world’s largest epidemic of Ebola virus disease is currently ongoing in West Africa, concentrated in the countries of Liberia, Sierra Leone, and Guinea. Ebola emerges in a human population after contact with an infected animal host and persists through human-to-human transmission. Persons with late stage illness are especially infectious. Ebola outbreaks are typically contained by outbreak investigation and patient isolation. But, as the current epidemic shows, containment may be very difficult to achieve in areas of high population density or where there is little health infrastructure.
During the second half of 2014, the West African nation of Liberia suffered the greatest rates of Ebola transmission. Slowing the spread of Ebola was found to be especially difficult after the virus reached the urban areas around Monrovia, particularly the township of West Point. The United States, other nations, and non-governmental organizations promised aid and developed a plan to improve Liberia’s health infrastructure, but many aspects of urban Ebola transmission were then unknown, including the relative importance of hospital- and community-acquired infection, how much hospital capacity must be increased to provide care for the anticipated patient burden, and what level patient of isolation would be required to contain the outbreak. To address these issues, we developed a model for Ebola transmission that accounted for the separate sites at which infection could occur, for instance in the home, in public places (particularly at funerals), or in health facilities. Based on information available by mid-October, it was not clear whether enough was being done to contain the epidemic in Liberia. But, through public vigilance and community participation, particularly the willingness of infected persons to be treated in health facilities and to allow safe handling of the bodies of the deceased, transmission dropped dramatically in the last quarter of the year. An updated version of our model developed in early December suggests that if these gains can be maintained then the epidemic may be over by the middle of 2015.
Medical Research: What should clinicians and patients take away from your report?
Dr. Drake: Our study found that one of the most important factors for containing the epidemic was the patient isolation rate. Our study suggests that early in the epidemic there was a race between the construction of new health facilities and the increase in new cases through infections acquired from persons treated in the community. Importantly, patient isolation requires both care-seeking on the part of the patient and the national capacity to care for patients safely. Public health depends on persons who suspect they may have been infected with Ebola virus to seek care as early as possible, particularly before symptoms become severe and the disease is at its most infectious. Early admission and access to supportive care also gives patients the greatest chance of survival. In hospitals in developed countries, where hygienic conditions prevail, safety precautions have been put in place for persons suspected of Ebola infection, and infection control procedures have been adopted, secondary transmission is extremely unlikely. Early hospitalization is therefore the most important consideration for any accidentally imported cases.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Drake: This study adopted a modeling approach based on the mathematical theory of branching processes. This approach enabled more accurate description of the uncertainty associated with epidemic progression than some other approaches currently in use. But, several technical problems remain to be solved to use these methods most effectively, including how best to estimate the key quantities of interest and to identify those factors that may be changing over time. These tasks are further complicated by the urgency of a developing epidemic and the need for continuous updating as information becomes available. Real time epidemic modeling and forecasting is an important area for further research investment.
Ebola Cases and Health System Demand in Liberia
John M. Drake , Affiliation: Odum School of Ecology, University of Georgia, Athens, Georgia, RajReni B. Kaul, Affiliation: Odum School of Ecology, University of Georgia, Athens, Georgia, Laura W. Alexander,Affiliation: Odum School of Ecology, University of Georgia, Athens, Georgia,
Suzanne M. O’Regan, Affiliation: Odum School of Ecology, University of Georgia, Athens, Georgia,
Andrew M. Kramer, Affiliation: Odum School of Ecology, University of Georgia, Athens, Georgia, J. Tomlin Pulliam, Affiliation: Odum School of Ecology, University of Georgia, Athens, Georgia, Matthew J. Ferrari, Affiliation: Department of Biology, Pennsylvania State University, State College, Pennsylvania, United States of America Andrew W. Park Affiliations: Odum School of Ecology, University of Georgia, Athens, Georgia, College of Veterinary Medicine, University of Georgia, Athens, Georgia, Published: January 13, 2015 DOI: 10.1371/journal.pbio.1002056