Ebola Virus in Sierra Leone Mutated at a Normal Rate

By Jamie Condliffe on at

Since the Ebola outbreak occurred in West Africa in 2014, researchers have feared that the virus had been able to evolve at a more rapid rate than usual. Now, an analysis of the virus reveals that it mutated at a perfectly normal rate in Sierra Leone, alleviating those fears.

A team of Chinese researchers, that has been working at a hospital in Sierra Leone since September 2014, has collected and analysed genome sequences from virus samples in patients they’ve treated. Bringing together 175 sequences from between September 28th and November 11th, the team has shown that the virus mutated at a rate very similar to observations made in the past.

Whilst there have been other genomes sequences of the virus made since the outbreak took hold in West Africa, those analyses had all been performed before the biggest growth phase of the outbreak in July and August. The fresh analysis shows that the Ebola virus, which is known to quickly and easily mutate, in fact developed into seven distinct-but-related sublineages in Sierra Leone. These were found to have emerged before August and reside in distinct geographical areas. The results are published in Nature.

Despite such branching, the lack of rapid mutation—which is the feature of the virus that caused concern that it could become more contagious or even airborne—allays concerns of many health workers. Sadly, the report also reminds us that 10,000 individuals have now been killed by the outbreak.

Mercifully, the outbreak has been declared to be over in Liberia by the World Health Organization. Guinea and Sierra Leone still await such good news. [Nature via Medical Express]

Image by USAID U.S. Agency for International Development under Creative Commons license