Friday, August 29, 2014

Ebola virus mutating rapidly as it spreads

Outbreak likely originated with a single animal-to-human transmission. 

On 24 May, Augustine Goba received a blood sample from a pregnant woman in Sierra Leone who had fallen ill after attending the funeral of an Ebola victim in Guinea. Twenty-four hours later, the test results came back positive. Goba, who directs a diagnostic lab at Kenema Government Hospital in Sierra Leone, had confirmed the country's first case of Ebola.

He and his colleagues have now decoded the genetic sequences of 99 Ebola viruses collected from 78 patients during the first 24 days of the epidemic in Sierra Leone. The work1, published online in Science, could help to inform the design of diagnostics, therapeutics and vaccines, says structural biologist Erica Ollmann Saphire of The Scripps Research Institute in La Jolla, California. “This paper is terrific,” she adds.

The Ebola epidemic in West Africa has already killed more than 1,400 people — including five of Goba's co-authors from Kenema. The paper is dedicated to their memory.

The sequence data, which were made publicly available by 31 July, constitute the largest collection of genetic information on Ebola ever to be released. To get them, the group collected leftover blood from samples taken for diagnostic tests in Kenema. They then used a chemical solution to deactivate the Ebola viruses, and sent the samples to be sequenced at the Broad Institute in Cambridge, Massachusetts.

The researchers sequenced the viral genomes from each sample an average of more than 2,000 times, allowing them track how the virus mutated as it spread from patient to patient. In April, researchers reported2 that they had sequenced data from Guinean patients' viruses. That team, however, produced one composite viral genome sequence for each patient, rather than individually sequencing different copies of the virus found in each patient, as in the work reported today.

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