Performed in less than a month, sequencing of the complete genome and subsequent phylogenetic analysis show that the virus present in Guinea forms a clade (variant) that is distinct from strains previously identified in the Democratic Republic of Congo and in Gabon.
Epidemiological investigations also linked the laboratory confirmed cases with the initial deaths recorded during the December 2013 outbreak.
On 2 April 2014, the World Health Organisation (WHO), in a communiqué published by the UN, reported that it had recorded 5 new cases of Ebola fever in Guinea. Since January, the total number of suspected and confirmed cases of Ebola fever in the present outbreak in Guinea is 127, with 83 deaths, according to WHO, which states that 35 cases were confirmed by laboratory testing.
The initial samples were analysed in Lyon in the Jean Mérieux-Inserm BSL-4 Laboratory directed by Hervé Raoul, Inserm Research Director, by the French National Reference Centre for Viral Haemorrhagic Fevers (attached to the Biology of Viral Emerging Infections Unit at the Institut Pasteur, directed by Sylvain Baize). A positive diagnosis was made.
Mobile BSL-4 Response
A mobile BSL-4 laboratory was deployed in Guinea to provide assistance with diagnosis in the field. This mobile laboratory was developed as part of a European project, “EMP4,” coordinated by German researchers, and in which the Jean Mérieux-Inserm BSL-4 Laboratory is the French partner.
The researchers were able to analyse blood samples from 20 patients. Various tests were conducted by the scientists in order to establish a specific identity card for the virus.
Viral RNA was extracted from the blood samples, and then amplified and sequenced. These sequences were finally compared to 48 already known complete Ebola virus genomes. According to results, the analysis showed 97% identity with strains identified in the Democratic Republic of Congo in 1976 and 2007, and in Gabon in 1994 and 1996.
A New Form of Ebola
“These results demonstrate that we are facing the emergence of a new “form” of this virus in Guinea,” explains Hervé Raoul, Director of the BSL-4 Laboratory. This form is common to cases discovered since the month of December.
It would appear that the epidemic originated from a single introduction from animal to human.
Apart from the present epidemic, these results show that the endemic area for Ebola virus is greater than previously known, and that as a consequence, West Africa should henceforth be considered an area of risk for Ebola virus. Measures aimed at preventing transmission from wild fauna to humans and quickly identifying such events if there is a recurrence must be put in place in Guinea, as well as in neighbouring countries.
Read the paper at the New England Journal of Medicine: Emergence of Zaire Ebola Virus Disease in Guinea — Preliminary Report.
Source: INSERM. Image: Jean Mérieux-Inserm BSL-4 Laboratory, Lyon. Credit: Inserm/Guénet François