In a large multi-disciplinary collaboration, researchers from the Viral Hemorrhagic Fever Consortium (VHFC) have published key findings on Lassa virus (LASV) evolution. The study, published in the August 2015 edition of Cell, shares unique insights into the origins and evolutionary dynamics of LASV. These findings were based on a dataset of almost 200 LASV sequences collected from clinical and rodent reservoir samples obtained in Nigeria and Sierra Leone between 2008 to 2013.
Like Ebola virus (EBOV), LASV can cause hemorrhagic fever in infected individuals, with case fatality rates in excess of 50%. However, unlike EBOV, LASV is endemic in Nigeria, Sierra Leone, Guinea, and Liberia, resulting in severe disease in tens of thousands of people annually, and represents a significant public health burden in the region.
By using next-generation sequencing, researchers were able to analyze the genomes of LASV samples and determine that the virus likely originated in modern-day Nigeria more than a thousand years ago, and spread into neighboring countries within the last several hundred years. The study also indicated that whereas the 2013-2015 epidemic of Ebola virus disease is sustained by human-to-human transmission, LASV infections mainly result from reservoir-to-human infections. While the clinical symptoms for the two diseases are quite similar, the viruses themselves are different. “Most new Ebola patients get infected from other patients, so the focus needs to be on isolation to break the chain,” says the study’s lead author Professor Kristian G. Andersen. “In Lassa, our focus needs to be on preventing the spillover event.”
Researchers from many institutions including Harvard University, Tulane University, The Scripps Research Institute, Irrua Specialist Teaching Hospital, and Kenema Government Hospital, contributed to the findings of this study.