Ebola Variant Identified in Guinea


On April 16, 2014, researchers from the Institut Pasteur and from Inserm (Jean Mérieux-Inserm BSL-4 Laboratory, Lyon) published an article in the New England Journal of Medicine, documenting their characterization of the Ebola virus currently epidemic in Guinea. The pathogen responsible for the epidemic has been initially identified as a variant of the Zaire Ebola virus. The identification was made on the basis of the complete genome sequence and a phylogenetic analysis. The results suggest that the virus identified in Guinea is a variant of the Ebola virus, distinct from strains already found in the Democratic Republic of Congo and Gabon. As of April 20, 2014 the Guinea Ministry of Health has reported 208 suspected and confirmed cases of Ebola, with 136 fatalities. Suspected cases in neighboring Liberia and Sierra Leone are being investigated.

One aspect of the current epidemic that is particularly worrying is the broad distribution of Ebola cases, spread hundreds of miles apart. It is believed that bats are a reservoir for the virus and can carry the virus great distances, thus the distribution of the Ebola virus may be much broader than just the areas where past outbreaks have occurred. The only comforting note here is that the spillover of the virus from wildlife to humans is unusual.

Ebola is a terrifying virus; it is highly pathogenic, readily transmissible, and kills 30 to 90 percent of its victims.  Symptoms include fever, severe diarrhea, vomiting, and hemorrhage. There is currently no treatment for it. This makes it a class 4 pathogen, requiring a bio-containment facility rated at BioSafety Level 4 (BSL-4) – the highest safety level possible – for handling it. Researchers working in a BSL-4 laboratory are required to wear full-body positive pressure personnel suits (“moon suits”). Very stringent safety measures are taken to avoid accidental release of the virus: multiple airlocks, electronically regulated to prevent both doors opening at once; showers, a vacuum room, and an ultraviolet light room (UV light is mutagenic, and used for sterilization purposes). Exhaust air leaving the lab is purified by a double absolute filtration system, and all wastes produced are totally inactivated.  A mobile BSL-4 lab has been deployed in Guinea to assist with the diagnosis of Ebola.

Researchers took blood samples from 20 patients, and ran various tests to establish the identity of the virus. RNA from the virus taken from the blood samples was amplified and its sequence determined, then compared with the sequences of 48 strains of Ebola that have already been sequenced.  The new Ebola virus has 97 percent of its genetic material in common with the strains identified previously in the Democratic Republic of Congo from 1976 and 2007, and in Gabon from 1994 and 1996. This indicates the Ebola virus identified in Guinea is a variant of the previously identified virus, according to Herve Raoul, who directs the BSL-4 laboratory – one that is common to the cases discovered since December of last year, but that does not represent a new strain with different biological properties. It is likely that the current form of the Ebola virus began with a single instance of animal to human transmission. The virus spreads through direct contact with a sick person’s blood or body fluids and by contact with contaminated objects or infected animals. Patients who have been infected with Ebola must be isolated, and direct contact with the victims of the virus must be avoided.

Travelers in areas at risk are advised to practice careful hygiene, avoiding contact with blood or body fluids of infected persons, or animals that might carry the disease. Health care workers are instructed to wear personal protective equipment (PPE) such as masks, gowns, gloves, and eye protection. Médecins sans Frontières (MSF/Doctors without Borders) is establishing isolation and treatment centers at the heart of the epidemic in Guinea. International aid agencies are implementing awareness campaigns in Liberia, and providing PPEs for healthcare workers.  The Institute Pasteur in Lyon, France is collaborating with other international partners to identify the Ebola variant and track its distribution in Guinea. The American Centers for Disease Control (CDC) has a team in Guinea, and another in Liberia, helping other organizations with the outbreak. The CDC also communicates regularly with the World Health Organization (WHO) and MSF to get updates on the outbreak.

By Laura Prendergast

Science Daily

Centers for Disease Control

New England Journal of Medicine

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