Ebola in West Africa: A quarter-million cases by the end of the year?

Ebola in West Africa: A quarter-million cases by the end of the year? HT: Crof.

Via Eurosurveillance, a very interesting (and worrying) analysis: Early transmission dynamics of Ebola virus disease (EVD), West Africa, March to August 2014. The discussion section: We have derived global and country-specific estimates of the R_t of EVD for the ongoing outbreak in West Africa. Our global estimates of the R_t appear to be continuously above one since early June, indicating that the epidemic has been steadily growing and has not been brought under control as of 26 August 2014. 

The country-specific estimates for Sierra Leone and Liberia were also above one, perhaps reflecting the increasing trend in cases in these countries since June. Our estimated reproduction numbers, broadly ranging from one to two, are consistent with published estimates from prior outbreaks in Central Africa [9,17]. Our estimates of R Our statistical analysis of the reproduction number of EVD in West Africa has demonstrated that the continuous growth of cases from June to August 2014 signalled a major epidemic, which is in line with estimates of the R_t above 1.0. Moreover, the timing of R_t reaching levels above one is in line with a concomitant surge in cases in Sierra Leone and Liberia.

In a worst-case hypothetical scenario, should the outbreak continue with recent trends, the case burden could gain an additional 77,181 to 277,124 cases by the end of 2014.

Although such numbers must be interpreted with caution (as they rest on an assumption of continued exponential growth within 2014, which is unlikely), our study supports the notion that the ongoing EVD epidemic must be regarded as a Public Health Emergency of International Concern [3]. This finding also implies that transnational spread of EVD might have hindered control efforts, suggesting that preparedness plans for potential case introductions is critical particularly for countries at high risk of EVD case importations [18] with suboptimal public health systems.

The transnational spread per person appears to have been reduced over time, but our most recent model estimates still suggest a non-negligible number of secondary cases arising from transnational spread.

Uncontrolled cross-border transmission could fuel a major epidemic to take off in new geographical areas (e.g. as seen in Liberia). Unaffected countries at risk of transnational spread should be on high alert for potential EVD introductions and be ready to launch comprehensive and timely containment responses to avert outbreaks.  Our analysis is not exempted of limitations.

First, the epidemic is ongoing in multiple geographical locations, and no simple mixing matrix can capture the complex geographical patterns of spread in the region. 

Second, cases may be under-ascertained, and hence reported cases may represent only a portion of the total number of infected individuals. However, our estimates of the reproduction number are not affected whenever the diagnosis and reporting rates have not dramatically changed over time. 

Third, the reporting delays are known to induce a downward bias in incidence in the latest observation, which can complicate real-time analyses.  Several studies have successfully addressed this bias [19-22], but we were unable to incorporate this delay into our analyses due to a lack of empirical data to characterise the reporting delay distribution.  

Despite the above-mentioned limitations, we believe that our findings are useful to demonstrate that the cases have been steadily growing in the last three months with an R_t above one.  

Close monitoring of this evolving epidemic should continue in order to assess the status of the outbreak in real time and guide control interventions in the region. Reviewing possible countermeasures for countries at risk of transnational spread [18] would be of utmost importance to confront the ongoing propagation of cases over time and space. 

Hmmm....Somehow i keep getting flashbacks to an article i read a short while ago, it becomes more realistic by the day! 

EBOLA - Is this the time to put West Africa under UN trusteeship?