Ebola numbers show response is currently inadequate to achieve containment

Global health officials are looking closely at the Ebola Virus “reproduction number,” which estimates how many people, on average, will catch the virus from each person stricken with Ebola. The epidemic will begin to decline when that number falls below one. A recent analysis estimated the number at 1.5 to 2.

To bring the epidemic under control, officials should ensure that at least 70 percent of Ebola-victim burials are conducted safely, and that at least 70 percent of infected people are in treatment, within 60 days, he said

In 60 days there will be about 100,000 cases so there need to be about 70,000 beds. The 17 facilities being built by the US military will be able to handle 1700.

Sierra Leone desperately needs 750 doctors, 3,000 nurses, 1,500 hygienists, counselors and nutritionists.

The reproduction number, or “R nought,” is a mathematical term that tells you how contagious an infectious disease is. Specifically, it’s the number of people who catch the disease from one sick person, on average, in an outbreak.

Even modest gains in lowering that reproduction number could give health officials and the military a better chance of controlling the epidemic. “Maybe we can bring it from two to 1.2 or 1.3, which would indicate that the number of new cases will be dramatically reduced, and that will give you time,” he said.

As the number of infections increases, so does the possibility that a person with Ebola will carry it to another country. This is known as an export.

“So we had two exports in the first 2,000 patients,” Frieden said in a recent interview. “Now we’re going to have 20,000 cases, how many exports are we going to have?”

Conventional methods of containing Ebola — isolating patients and doing contact tracing of people who might be exposed — lower the rate of new infections until finally the epidemic burns itself out. That has been the case in all previous outbreaks of Ebola, although no outbreak has ever been nearly as extensive as this one.

More trained people are needed to enable effective isolation, contact tracing and containment.

Mobilization should target the numbers in 60 days. Assume 100,000-200,000 cases need to be contained and get ramped up for that number. The current identified cases are an underestimate because people do not show symptoms for 4-21 days. There is widespread under-reporting of new cases, and that the situation in Liberia, and in Monrovia in particular,
continues to deteriorate from week to week.

PLOS – Estimating the Reproduction Number of Ebola Virus (EBOV) During the 2014 Outbreak in West Africa

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 indicates that in Guinea and Sierra Leone the effective reproduction number might have dropped to around 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.

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