News Release

Thursday, March 26, 2015

NIH study finds no evidence of accelerated Ebola virus evolution in West Africa

The Ebola virus circulating in humans in West Africa is undergoing relatively few mutations, none of which suggest that it is becoming more severe or transmissible, according to a National Institutes of Health study in Science. The study compares virus sequencing data from samples taken from patients in Guinea (March 2014), Sierra Leone (June 2014) and Mali (November 2014).

“The Ebola virus in the ongoing West African outbreak appears to be stable—that is, it does not appear to be mutating more rapidly than viruses in previous Ebola outbreaks, and that is reassuring,” said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), part of NIH. “We look forward to additional information to validate this finding, because understanding and tracking Ebola virus evolution are critical to ensuring that our scientific and public health response keeps pace.”

Obtaining virus samples for analysis was challenging for researchers during the outbreak. The NIAID study published today relies on data from the Guinea and Sierra Leone cases as well as samples from two case clusters in Mali obtained from the International Center for Excellence in Research (ICER) located in Bamako. NIAID and the Malian government have been partners in the ICER since 2002. The Mali case clusters originated from people who became infected in Guinea and traveled to Mali, where they were diagnosed.

Today’s study, from NIAID’s Rocky Mountain Laboratories, finds that there appear to be no genetic changes that would increase the virulence or change the transmissibility of the circulating Ebola virus, and that despite extensive human-to-human transmission during the outbreak, the virus is not mutating at a rate beyond what is expected. Further, they say, based on their data it is unlikely that the types of genetic changes thus far observed would impair diagnostic measures, or affect the efficacy of candidate vaccines or potential virus-specific treatments.

As of March 11, the World Health Organization listed more than 24,000 confirmed, suspected or probable cases of Ebola virus disease in West Africa, with about 10,000 deaths.

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T Hoenen, et al. Mutation rate and genotype variation of Ebola virus from Mali case sequences. Science DOI: 10.1126/science.aaa5646 (2015).