Ebola virus disease 2013-2014 outbreak in west Africa: an analysis of the epidemic spread and response

Abstract

The Ebola virus epidemic burst in West Africa in late 2013, started in Guinea, reached in a few months an alarming diffusion, actually involving several countries (Liberia, Sierra Leone, Nigeria, Senegal, and Mali). Guinea and Liberia, the first nations affected by the outbreak, have put in place measures to contain the spread, supported by international organizations; then they were followed by the other nations affected. In the present EVD outbreak, the geographical spread of the virus has followed a new route: the achievement of large urban areas at an early stage of the epidemic has led to an unprecedented diffusion, featuring the largest outbreak of EVD of all time. This has caused significant concerns all over the world: the potential reaching of far countries from endemic areas, mainly through fast transports, induced several countries to issue information documents and health supervision for individuals going to or coming from the areas at risk. In this paper the geographical spread of the epidemic was analyzed, assessing the sequential appearance of cases by geographic area, considering the increase in cases and mortality according to affected nations. The measures implemented by each government and international organizations to contain the outbreak, and their effectiveness, were also evaluated.

Figure 1

Ebola virus representation. The virion and main proteins are represented. The see-through window in virion shows the negative-sense RNA single-stranded genome covered by nucleoproteins and VP30.

Figure 2

Time trend of compatible EVD cases (confirmed, white bars; probable and suspected, grey bars) in affected countries Guinea (a), Liberia (b), and Sierra Leone (c) according to the periods reported in Table 1. Red numbers over each bar represent the total amount of all compatible cases (confirmed, probable, and suspected) for each period.

Figure 3

Time trend of compatible EVD deaths (confirmed, white bars; probable and suspected, grey bars) in affected countries Guinea (a), Liberia (b), and Sierra Leone (c) according to the periods reported in Table 1. Red numbers over each bar represent the total amount of all compatible deaths (confirmed, probable, and suspected) for each period. ^* in (a) indicates that in the relative WHO reports the distinction between confirmed and unconfirmed cases was not made. ^** in (b) indicates that in the relative WHO report notices about the cases progression in Liberia were not reported.

Figure 4

(a) Affected nations (Guinea, Liberia, and Sierra Leone) divided in the respective administrative areas. Guinea, light grey, 34 prefectures, numbers from 1 to 34; Liberia, 15 countries, mild grey, Roman numerals from I to XV; Sierra Leone, dark grey, 14 districts, letters from a to n. Stars indicate the capital cities; red star, Conakry; green star, Monrovia; blue star, Freetown. (b) In the panel the regions in which each country is suborganized are reported.

Figure 5

Progressive geographical spread of the EVD outbreak from period 2 to period 15 (for period 1, until the publication of the first WHO report, consolidated geographical details have not been identified). During periods 4, 5, and 6 and during the periods 10-11 there were no progressions in the geographical spread. The periods are reported according to Table 1. Areas barely affected by the epidemic are shown in yellow; the areas already interested with the progression of time are shown in red. Only areas progressively affected were numbered according to administrative areas reported in Figure 4. Solid arrow indicates a spreading into new areas during subsequent periods, according to Table 1. Intermittent arrow indicates no EVD diffusion in new areas for a number of periods according to the arrows amount.