Dynamics and control of Ebola virus transmission

[BostonRN]

Dynamics and control of Ebola virus transmission in
Montserrado, Liberia: a mathematical modelling analysis

www.thelancet.com/infection Published online October 24, 2014


Joseph A Lewnard*, Martial L Ndeff o Mbah*, Jorge A Alfaro-Murillo, Frederick L Altice, Luke Bawo, Tolbert G Nyenswah, Alison P Galvani

Summary
Background A substantial scale-up in public health response is needed to control the unprecedented Ebola virus
disease (EVD) epidemic in west Africa. Current international commitments seek to expand intervention capacity in
three areas: new EVD treatment centres, case ascertainment through contact tracing, and household protective kit
allocation. We aimed to assess how these interventions could be applied individually and in combination to avert
future EVD cases and deaths.

Methods We developed a transmission model of Ebola virus that we fitted to reported EVD cases and deaths in
Montserrado County, Liberia. We used this model to assess the effectiveness of expanding EVD treatment centres,
increasing case ascertainment, and allocating protective kits for controlling the outbreak in Montserrado. We
varied the efficacy of protective kits from 10% to 50%. We compared intervention initiation on Oct 15, 2014,
Oct 31, 2014, and Nov 15, 2014. The status quo intervention was defi ned in terms of case ascertainment and
capacity of EVD treatment centres on Sept 23, 2014, and all behaviour and contact patterns relevant to transmission
as they were occurring at that time. The primary outcome measure was the expected number of cases averted by
Dec 15, 2014.

Findings We estimated the basic reproductive number for EVD in Montserrado to be 2·49 (95% CI 2·38–2·60).
We expect that allocating 4800 additional beds at EVD treatment centres and increasing case ascertainment fi ve-fold
in November, 2014, can avert 77 312 (95% CI 68 400–85 870) cases of EVD relative to the status quo by Dec 15, 2014.
Complementing these measures with protective kit allocation raises the expectation as high as 97 940 (90 096–105 606)
EVD cases. If deployed by Oct 15, 2014, equivalent interventions would have been expected to avert 137 432
(129 736–145 874) cases of EVD. If delayed to Nov 15, 2014, we expect the interventions will at best avert 53 957
(46 963–60 490) EVD cases.

Interpretation The number of beds at EVD treatment centres needed to eff ectively control EVD in Montserrado
substantially exceeds the 1700 pledged by the USA to west Africa. Accelerated case ascertainment is needed to
maximise eff ectiveness of expanding the capacity of EVD treatment centres. Distributing protective kits can further
augment prevention of EVD, but it is not an adequate stand-alone measure for controlling the outbreak. Our findings
highlight the rapidly closing window of opportunity for controlling the outbreak and averting a catastrophic toll of
EVD cases and deaths.

Funding US National Institutes of Health.


http://www.thelancet.com/journals/laninf/article/PIIS1473-3099(14)70995-8/fulltext

 

[BostonRN]

Re: Dynamics and control of Ebola virus transmission

This is a concerning interpretation and all I hear from press releases is that we have it under control and we are not at risk. It seems the concern is to make sure that nobody over reacts and at the same time this study is warning us about under reacting......

We are all connected and at this rate and extent it is only a matter of time.


"Continued spread of Ebola virus threatens affected west African nations and the rest of the world, making outbreak containment a global health priority. Because vaccines to prevent EVD remain unavailable, we urge a rapid and immediate scaling up of currently available non-pharmaceutical intervention strategies to minimize the occurrence of new EVD cases and deaths. Perhaps most alarming is that, although we might still be within the midst of what will ultimately be viewed as the early phase of the current EVD outbreak, the window of opportunity for aversion of calamitous repercussions from an initially delayed and insufficient response is diminishing rapidly. Our predictions suggest that current commitments are grossly inadequate to provide beds for all infected individuals, even only considering near-term growth of the epidemic in Montserrado. Although transmission reduction afforded through provision of home protection kits could have a limited effect on mitigation of temporary bed shortages, our results suggest transmission of Ebola virus will not be curtailed without much greater commitment to improvement of all preventive measures that international aid is currently attempting to address."