Tuesday, September 2, 2014

Ebola is not yet under control in any West African country

In a recent article entitled Estimating the reproduction number of Ebola virus (EBOV) during the 2014 outbreak in West Africa, Christian L. Althaus, a post-doctoral research fellow at Institute of Social and Preventive Medicine at the University of Bern, provides an optimistic and unrealistic assessment of the Ebola outbreak in West Africa. In the abstract, Althaus implies that the Ebola outbreaks in Guinea and Sierra Leone were under control by the end of May and July 2014, respectively. Elsewhere in the text he contradicts the abstract and states:
"This results in a different decrease of the effective reproduction number, Re, after the outbreaks started in each country [Guinea. Liberia, Sierra Leone]. While Re dropped below unity in Guinea and Sierra Leone by end-August 2014, the model suggests that control interventions were not successful in reducing Re in Liberia."
Based on the World Health Organization (WHO) comments that the number of Ebola cases are grossly underestimated (WHO link, WHO link), there is no evidence to suggest that as of September 1, 2014 the effective reproductive rate has dropped below 1 in either Guinea or Liberia nor is there evidence of a concomitant decrease in new cases.

Althaus also states:
"In particular, I assumed that the transmission rate decays exponentially due to control measures after the appearance of the first infectious case."
With more than 240 health care workers infected during this outbreak (WHO link) and health care facilities overwhelmed, there is no reason to assume that adequate control measures are in place. Without adequate control measures, transmission rates will not decrease exponentially in these countries in the near future and the current data do not suggest that the reproductive number in any of these countries is less than 1. At this time, the Ebola outbreak in West Africa is continuing to grow and is not yet under control.

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