Disease modelers project a rapidly rising toll from Ebola

[Pathfinder]

Disease modelers project a rapidly rising toll from Ebola

By Kai Kupferschmidt
31 August 2014 10:00 am

Alessandro Vespignani hopes that his latest work will turn out to be wrong. In July, the physicist from Northeastern University in Boston started modeling how the deadly Ebola virus may spread in West Africa. Extrapolating existing trends, the number of the sick and dying mounts rapidly from the current toll?more than 3000 cases and 1500 deaths?to around 10,000 cases by September 24, and hundreds of thousands in the months after that. ?The numbers are really scary,? he says?although he stresses that the model assumes control efforts aren't stepped up. "We all hope to see this NOT happening," Vespigani writes in an e-mail.
...
If the disease keeps spreading as it has, most of the modelers Science talked to say WHO?s estimate will turn out to be conservative. ?If the epidemic in Liberia were to continue in this way until the 1st of December, the cumulative number of cases would exceed 100,000,? predicts Althaus. Such long-term forecasts are error-prone, he acknowledges. But other modelers aren?t much more encouraging. Caitlin Rivers of the Virginia Polytechnic Institute and State University in Blacksburg expects roughly 1000 new cases in Liberia in the next 2 weeks and a similar number in Sierra Leone.

Vespignani has analyzed the likelihood that Ebola will spread to other countries. Using data on millions of air travelers and commuters, as well as mobility patterns based on data from censuses and mobile devices, he has built a model of the world, into which he can introduce Ebola and then run hundreds of thousands of simulations. In general, the chance of further spread beyond West Africa is small, Vespignani says, but the risk grows with the scale of the epidemic. Ghana, the United Kingdom, and the United States are among the countries most likely to have an introduced case, according to the model. (Senegal, which reported its first Ebola case last week, was in his top ten countries, too.)
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Full text:
http://news.sciencemag.org/health/2014/08/disease-modelers-project-rapidly-rising-toll-ebola

 

[mac68DC]

Re: Disease modelers project a rapidly rising toll from Ebola

"The challenge varies by country, Althaus says. “In Guinea and Sierra Leone, Re is close to 1 and the outbreak could be stopped if interventions improve a bit.” In Liberia, Re has been near 1.5 the whole time. “That means work is only just beginning there.” But Meltzer says there is no reason to believe the situation is any better in Sierra Leone. “We are not seeing any change in the rate of the accumulation of cases,” he says. "

I don't trust these numbers and models, nor the official CDC/WHO counts.

The only way you can get accurate numbers are if:

• People trust the system and self report.
• Your intake and bed capacity can handle all of the incoming suspected cases.

I strongly suspect that the numbers reported are a representation of patient capacity and not much more. What is being reported is basically the expansion of the medical system to handle cases. I am betting most of these places are consistently at 100% capacity and turning lots of people away.

We also know many people simply do not self report.

If you want a more realistic number, set the baseline at where you think capacity was reached (June? July?), and apply the r0 you think applies. From there, project out. This still ignores those that did not self report (or could have been uncovered by intelligence/surveillance), but its the best you are going to get imo.

Edit: Actually, I say take the mid July case count and x by 4. (25% report rate) 1000 x 4 = 4000

So we could be looking at about 16,000 cases right now.

 

[mac68DC]

Re: Disease modelers project a rapidly rising toll from Ebola

Estimating the reproduction number of Ebola virus (EBOV) during the 2014 outbreak in West Africa
Cornell Univ Library
http://arxiv.org/abs/1408.3505
(Submitted on 15 Aug 2014 (v1), last revised 27 Aug 2014 (this version, v3))


"The 2014 Ebola virus (EBOV) outbreak in West Africa is the largest outbreak of the genus Ebolavirus to date. To better understand the spread of infection in the affected countries, it is crucial to know the number of secondary cases generated by an infected index case in the absence and presence of control measures, i.e., the basic and effective reproduction number. In this study, I describe the EBOV epidemic using an SEIR (susceptible-exposed-infectious-recovered) model and fit the model to the most recent reported data of infected cases and deaths in Guinea, Sierra Leone and Liberia. The maximum likelihood estimates of the basic reproduction number are 1.51 (95% confidence interval [CI]: 1.50-1.52) for Guinea, 2.53 (95% CI: 2.41-2.67) for Sierra Leone and 1.59 (95% CI: 1.57-1.60) for Liberia. The model shows that in Guinea and Sierra Leone the effective reproduction number dropped below unity by the end of May and July 2014, respectively. In Liberia, however, the model estimates no decline in the effective reproduction number by end-August 2014. This suggests that control efforts in Liberia need to be improved substantially in order to stop the current outbreak."

These numbers seem to make more sense..

 

[mac68DC]

Re: Disease modelers project a rapidly rising toll from Ebola

 

[Ronan Kelly]

Re: Disease modelers project a rapidly rising toll from Ebola

Modeling the Impact of Interventions on an Epidemic of Ebola in Sierra Leone and Liberia
OCTOBER 16, 2014 ? RESEARCH
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AUTHORS
Caitlin Rivers
Eric Lofgren
Madhav Marathe
Stephen Eubank
Bryan Lewis
ABSTRACT

Background: An Ebola outbreak of unparalleled size is currently affecting several countries in West Africa, and international efforts to control the outbreak are underway. However, the efficacy of these interventions, and their likely impact on an Ebola epidemic of this size, is unknown. Forecasting and simulation of these interventions may inform public health efforts.

Methods: We use existing data from Liberia and Sierra Leone to parameterize a mathematical model of Ebola and use this model to forecast the progression of the epidemic, as well as the efficacy of several interventions, including increased contact tracing, improved infection control practices, the use of a hypothetical pharmaceutical intervention to improve survival in hospitalized patients.

Findings: Model forecasts until Dec. 31, 2014 show an increasingly severe epidemic with no sign of having reached a peak. Modeling results suggest that increased contact tracing, improved infection control, or a combination of the two can have a substantial impact on the number of Ebola cases, but these interventions are not sufficient to halt the progress of the epidemic. The hypothetical pharmaceutical intervention, while impacting mortality, had a smaller effect on the forecasted trajectory of the epidemic.

Interpretation: Near-term, practical interventions to address the ongoing Ebola epidemic may have a beneficial impact on public health, but they will not result in the immediate halting, or even obvious slowing of the epidemic. A long-term commitment of resources and support will be necessary to address the outbreak.

...


Full paper open access here; http://currents.plos.org/outbreaks/...pidemic-of-ebola-in-sierra-leone-and-liberia/

 

[Toaster2]

Re: Disease modelers project a rapidly rising toll from Ebola

The paper states thag there is an R0 of 1, 78 and 2.22 in two of the countries. For flu the pandemic threshold was around 1, 6 -am I correct ?

Is an R0 for ebola a similar indicator for worldwide spread as it is for flu, or does it have to be higher as the mode of transmission is different ?

 

[Toaster2]

Re: Disease modelers project a rapidly rising toll from Ebola

The paper states thag there is an R0 of 1, 78 and 2.22 in two of the countries. For flu the pandemic threshold was around 1, 6 -am I correct ?

Is an R0 for ebola a similar indicator for worldwide spread as it is for flu, or does it have to be higher as the mode of transmission is different ?

Note added: the paper also shows the impact intervention can have, which paints a much more positive picture.

 

[Graupel]

Re: Disease modelers project a rapidly rising toll from Ebola

New paper out today with slightly different assumptions, with a far more grim prognosis:

Near-term, practical interventions to address the ongoing Ebola epidemic may have a beneficial impact on public health, but they will not result in the immediate halting, or even obvious slowing of the epidemic.


http://currents.plos.org/outbreaks/...pidemic-of-ebola-in-sierra-leone-and-liberia/

 

[AlaskaDenise]

Re: Disease modelers project a rapidly rising toll from Ebola

last sentence in discussion section of Graupel's above referenced paper:

The ongoing Ebola epidemic in West Africa demands international action, and the results of this study support that many of the interventions currently being implemented or considered will have a positive impact on reducing the burden of the epidemic. However, these results also suggest that the epidemic has progressed beyond the point wherein it will be readily and swiftly addressed by conventional public health strategies. The halting of this outbreak will require patient, ongoing efforts in the affected areas and the swift control of any further outbreaks in neighboring countries.

.