While an Ebola epidemic has been raging in West Africa since March 2014, an outbreak of this haemorrhagic fever occurred in the Democratic Republic of the Congo (DRC) in August, leaving fears over the virus' spread to Central Africa. A study by the IRD, the Institut Pasteur, the CNRS, the CIRMF in Gabon, the INRB in DRC and the WHO, published in the New England Journal of Medicine on 16 October 2014, confirms that it is an Ebola epidemic. However, this particular epidemic is due to a local strain of the virus, different from the one rife in the West of the continent. While this result shows the two epidemics are not linked, it illustrates the speed at which the disease has emerged. It is therefore urgent that we understand just how the disease is spread.
With the world's eyes focused on West Africa, where several countries have been affected since March 2014 by the most serious Ebola epidemic ever witnessed, the WHO reported another outbreak in the North of the Democratic Republic of the Congo on 24 August. It was therefore essential to verify whether this second epidemic stemmed from that of West Africa, indicating its spread to Central Africa.
A different strain
Researchers from the IRD, the Institut Pasteur, the CNRS, the CIRMF in Gabon and the INRB in the DRC, in collaboration with WHO experts, reveal that it is a new outbreak of haemorrhagic fever, separate from the West-African outbreak. The CIRMF has performed whole genome sequencing of the virus responsible using a high-throughput sequencer that is unique to Sub-Saharan Africa. It confirms that it is a virus from the Ebola species, but shows that the Congolese strain is different from the one in West Africa. Moreover, it appears to be very similar to those that ravaged in the DRC and Gabon between 1995 and 1997.
A contained epidemic
This result means that the Congolese outbreak is due to a local viral strain, which has been controlled. This epidemic began on 26 July 2014 when a woman fell ill a few days after cutting up a monkey found dead in the forest. To date, 70 cases have been confirmed, including 42 deaths, giving a fatality rate of around 60%, similar to that observed in West Africa. The epidemic peak was observed in the week of 24 August 2014. Thanks to the protection measures implemented by the Congolese health authorities - isolation of patients, protection of medical staff, instructing the populations to avoid all body contact - the epidemic now appears to be contained.
This recent rise in Ebola epidemics shows that the likelihood of the virus being passed on from animal reservoir to humans is increasing. We therefore urgently need to gain a better understanding of the ways in which the virus circulates (seasonal or other) within its natural reservoir and the factors that govern the virus' transfer from one animal species to another or to humans. Better knowledge of these parameters would enable alert thresholds to be defined and epidemics to be predicted, which could prove invaluable to the rapid implementation of control measures.