Public Release: 

The Lancet Infectious Diseases: Study predicts that current international commitments will not contain Ebola outbreak in Montserrado, Liberia

The Lancet

New modeling research, published in The Lancet Infectious Diseases journal, has found that the number of Ebola treatment center beds and other measures needed to control the epidemic in Montserrado County, Liberia substantially exceeds the total pledged by the international community to date.

The research shows that, without expanded control efforts, up to 170996 total reported and unreported Ebola cases, and 90122 deaths are projected in Montserrado by 15 December, 2014. The study estimates that of these, 42669 cases and 27175 deaths will have been reported by that time.

However, rapid scale-up of control measures starting on 31 October, including 4800 additional hospital beds, a fivefold increase in the speed with which cases are detected (for example, through contact tracing), and allocating protective kits for home care, could prevent as many as 97940 cases by 15 December.

Further delays in expanding these interventions would greatly limit their effectiveness. For example, if delayed to 15 November, at best just over half as many (53957) cases would be averted.

"Our predictions highlight the rapidly closing window of opportunity for controlling the outbreak, and averting a catastrophic toll of new Ebola cases and deaths in the coming months" [3], warns Alison Galvani, senior author and Professor of Epidemiology at the Yale School of Public Health, USA.

Professor Galvani and colleagues used mathematical modelling to evaluate the ability of control interventions (ie, new treatment centres to isolate and treat Ebola patients, case finding through contact tracing, and protective kits to help household-based isolation of infected individuals) to control the Ebola outbreak in Montserrado during various time periods.

The researchers estimate that the reproductive number (R0, the average number of infections caused by a single infected individual) in Montserrado is 2•49. They predict that the addition of 4800 treatment beds, alongside increasing case detection fivefold in November, could prevent 77312 cases by 15 December, 2014. Additionally, a complementary strategy of allocating protective kits could bring the number of deaths averted up to 97940 cases in total.

Had all three interventions been implemented two weeks earlier, before 15 October, 2014, they would have been expected to prevent up to 137432 total reported and unreported cases.

According to Professor Galvani, "While the window of opportunity for timely control of the Ebola outbreak has passed, the risk of catastrophic devastation both in West Africa and beyond has only just begun. While vaccines to prevent Ebola remain unavailable, our study urges a rapid and immediate scaling-up of all currently available non-pharmaceutical intervention strategies to minimize the occurrence of new cases and deaths" [3].

Writing in a linked Comment, Professor David Fisman and Ashleigh Tuite, from the University of Toronto's Dalla Lana School of Public Health in Canada, explain why the study's predictions are useful: "The growth of this epidemic fits so well with mathematical epidemiological ideas that it seems torn from the pages of a textbook. And thus, even as the current Ebola epidemic wastes lives, devastates economies, and causes widespread fear, it follows a seemingly well behaved epidemiological process, readily understood through the use of mathematical modelling".

They add that, "The urgency of timely intervention in the Ebola epidemic cannot be overstated. The reason is one of simple mathematics: if R0 in this region is around 2•5, as Lewnard and colleagues estimate, incidence in every successive epidemic generation will increase by 150%...Researchers have asserted that the epidemic is proceeding in virus time, with a response on bureaucrat time. From a global perspective, controlling the Ebola epidemic in west Africa is not only a humanitarian duty but also a matter of crude self-interest. [This study] shows that intervention will only be meaningful if it is timely, and so far it has not been."

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NOTES TO EDITORS:

The study is funded by the US National Institutes of Health.

[1] Ebola-infected travellers from this region, home to Monrovia, Liberia's capital city, have already caused an outbreak of at least 19 cases in Nigeria.

[2] On September 16, 2014, the USA announced the construction of 17 new Ebola Treatment Centres to isolate and treat 1700 patients. As of 15 October, 2014, Liberia reports that only six out of 28 planned Ebola Treatment Centres are operational, providing 620 out of 2930 planned beds http://apps.who.int/iris/bitstream/10665/136508/1/roadmapsitrep15Oct2014.pdf?ua=1

[3] Quotes direct from author and cannot be found in text of Article.

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