New study sheds light on source of Nigeria’s Lassa fever outbreak

Public health officials monitoring a Lassa fever outbreak in Nigeria since January 2018 have been on edge for much of the year as the hemorrhagic fever spread among more than 500 people and killed 134 through the end of September. The outbreak, the largest in Nigeria’s history, has had experts concerned that the virus had mutated into a super-bug and was spreading from person to person.

A new study, however, allays those fears, according to an October 17, 2018 article in Nature. The study marks the most extensive and rapid genomic analysis of the Lassa virus conducted to date and revealed a significant amount of genetic diversity among 129 virus genomes isolated from patients this year, and 91 others collected from Nigeria between 2015 and 2017. The diversity indicated that Lassa has not been spreading between people, but instead has been fueled by exposure to rats.

In addition to shining light on the potential source of the outbreak, the findings could help scientists improve diagnostics, a critical component to stemming future outbreaks.

“What we’d like to see in the future is that four days after an infection emerges, we learn its genomic sequence and make a diagnostic immediately,” said Pardis Sabeti, a professor of immunology and infectious diseases at Harvard T.H. Chan School of Public Health and an institute member of the Broad Institute of MIT and Harvard. “We are always preparing ourselves for the possibility that Lassa virus will pick up a mutation that lets it transmit readily from human to human.”

Read the Nature article: Nigeria’s largest Lassa fever outbreak sparked by rats

Read the Broad Institute press release: Rapid genomic sequencing of Lassa virus in Nigeria enabled real-time response to 2018 outbreak