CDC projects huge increase in number of Ebola cases in West Africa until 70% of new cases confined to Ebola treatment centers or equivalent

For the latest projections of new cases of Ebola, under varying assumptions as to the date of initiation of effective interventions in West Africa, see

(1) Centers for Disease Prevention, “Estimating the Future Number of Cases in the Ebola Epidemic — Liberia and Sierra Leone, 2014–2015,” Morbidity and Mortality Weekly Report (MMWR), Supplements, September 26, 2014 / 63(03);1-14

(2) Centers for Disease Control, Summary of (1).

The Summary of the report states the following:

This week’s MMWR, Estimating the Future Number of Cases in the Ebola Epidemic—Liberia and Sierra Leone, 2014–2015, estimates the future number of cases if current trends continue. The MMWR also adjusts the number of cases based on estimated underreported cases.

By September 30, 2014, CDC estimates that there will be approximately 8,000 cases, or as high as 21,000 cases if corrections for underreporting are made.
Without additional interventions or changes in community behavior, CDC estimates that by January 20, 2015, there will be a total of approximately 550,000 Ebola cases in Liberia and Sierra Leone or 1.4 million if corrections for underreporting are made.

Cases in Liberia are currently doubling every 15-20 days, and those in Sierra Leone and Guinea are doubling every 30-40 days.
Halting the epidemic requires that approximately 70% of Ebola cases be cared for in Ebola Treatment Units or, if they are at capacity, at home or in a community setting in which there is a reduced risk of disease transmission and safe burials are provided.

Key Messages

If conditions remain unchanged, the situation will rapidly become much worse.
We know how to control and eventually stop the epidemic. Halting the epidemic requires placing up to 70% of patients into either an Ebola Treatment Unit or in a community setting in which the risk of disease transmission is reduced and safe burials are provided.

The cost of delay will be devastating. The number of cases is doubling about every 20 days. Every month of delay in reaching the 70% target will increase the number of patients, which means more cases and more deaths and the need for even more beds and other resources.

Questions and Answers

What is the basis of these estimates?

In producing the estimates, CDC researchers assumed that current conditions of disease transmission would continue without changes. The main driver of these estimates is that, in Sierra Leone and Liberia combined, reported cases are doubling approximately every 20 days.

What does “cases were corrected for underreporting by a factor of 2.5” mean?

For every case reported and recorded in publicly available case counts, an additional 1.5 cases are not recorded. In order to get an estimate of actual cases, we multiplied the reported number of cases by 2.5.

How was the factor of 2.5 calculated?

The factor of 2.5 was calculated by taking estimates of beds-in-use, computed by using CDC’s EbolaResponse modeling tool, and comparing these estimates to an expert opinion of actual beds-in-use (for a given day: August 28, 2014). The difference between the estimated beds-in-use and the estimated actual reported beds-in-use is a potential underreporting correction factor (1.5 more beds were being used than what the model estimates).

How accurate are the estimates (using uncorrected or corrected data)?

They are only estimates, and CDC cannot guarantee their accuracy; however, the estimates illustrate that if conditions remain unchanged, the situation will rapidly become much worse. As such, the estimates are a warning and a call to action.

What must happen to ensure that these estimates do not occur?

Effective interventions need to occur quickly, including appropriate disease control methods, communication, changes in community behavior, and adequate resources (such as staff, beds, equipment, supplies). The EbolaResponse tool also estimates the number of beds that would be required in hospitals/Ebola Treatment Units. Details and resources required for enhanced protection to minimize disease transmission is not the purpose of this model.

What aspects are contributing to the spread of Ebola? Why are cases doubling every approximately 20 days?

We do not have appropriate data to say specifically why this is occurring.

We know, from earlier Ebola outbreaks, what factors contribute to the spread of Ebola and we use that information to fit the available data to our model. What we do know is that the cases are increasing rapidly, and more needs to be done quickly.

Does the model suggest that there is something different about this virus compared to other Ebola outbreaks?

We used information from past outbreaks to inform our assumptions about the period of infectivity and the time between exposure and illness, and we were able to “fit” the model to the data to date. The model does not provide any evidence that the virus is transmitted differently than during past outbreaks.

Have you evaluated what would happen if people made changes in burial practices?

Yes, the model can be used to evaluate the potential effect of a variety of changes. The outbreak could be stopped if 70% of Ebola cases are cared for in Ebola Treatment Units or, if they are at capacity, at home or in a community setting such that there is a reduced risk of disease transmission, assuming that safe burial practices are in place in both settings.

The key to containing the epidemic is the confinement of 70% of new cases to Ebola treatment centers or their equivalent.

That is why fast and urgent assistance to Liberia, Sierra Leone, and Guinea is of the utmost importance.

For example, while the U.S. has promised to send 3,000 military personnel to the afflicted areas in West Africa, current information suggests that the personnel will not be fully deployed before the epidemic spirals out of control.

Speed is of the the essence. Fast deployment of medical personnel, Ebola treatment centers, and related human resources and equipment may in the end save more lives than a larger assistance effort that takes months to implement on the ground.

The Trenchant Observer

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The Observer
"The Trenchant Observer" is edited and published by The Observer, an international lawyer who has taught International Law, Human Rights, and Comparative Law at major U.S. universities, including Harvard, Brandeis, the University of Pittsburgh, and the University of Kansas. He is a former staff attorney at the Inter-American Commission on Human Rights of the Organization of American States (IACHR), where he was in charge of Brazil, Haiti, Mexico and the United States, and also worked on complaints from and reports on other countries including Argentina, Chile, Uruguay, El Salvador, Nicaragua, and Guatemala. As an international development expert, he has worked on Rule of Law, Human Rights, and Judicial Reform in a number of countries in Latin America, the Caribbean, Africa, the Middle East, South Asia, and the Russian Federation. In the private sector, The Observer has worked as an international attorney for a leading national law firm and major global companies, on joint ventures and other matters in a number of countries in Europe (including Russia and the Ukraine), throughout Latin America and the Caribbean, and in Australia, Indonesia, Vietnam, China and Japan. The Trenchant Observer blog provides an unfiltered international perspective for news and opinion on current events, in their historical context, drawing on a daily review of leading German, French, Spanish and English newspapers as well as the New York Times, the Wall Street Journal, the Washington Post, and other American newspapers, and on sources in other countries relevant to issues being analyzed. The Observer speaks fluent English, French, German, Portuguese and Spanish, and also knows other languages. He holds an S.J.D. or Doctor of Juridical Science in International Law from Harvard University, and a Doctor of Law (J.D.) and a Master of the Science of Law (J.S.M.), from Stanford University. As an undergraduate, he received a Bachelor of Arts degree, also from Stanford, where he graduated “With Great Distinction” (summa cum laude) and received the James Birdsall Weter Prize for the best Senior Honors Thesis in History. In addition to having taught as a Lecturer on Law at Harvard Law School, The Observer has been a Visiting Scholar at Harvard University's Center for International Affairs (CFIA). His fellowships include a Stanford Postdoctoral Fellowship in Law and Development, the Rómulo Gallegos Fellowship in International Human Rights awarded by the Inter-American Commission on Human Rights, and a Harvard MacArthur Fellowship in International Peace and Security. Beyond his articles in The Trenchant Observer, he is the author of two books and numerous scholarly articles on subjects of international and comparative law. Currently he is working on a manuscript drawing on the best articles that have appeared in the blog.

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