Lassa fever surge not linked to single strain or increased human transmission

A genomic analysis published in The New England Journal of Medicine this week revealed that an outbreak of Nigerian Lassa fever cases this year was not caused by any single virus strain or fueled by increased human-to-human transmission.

The analysis followed an unusual surge in Lassa fever cases reported by the Nigeria Centre for Disease Control (NCDC). In all, 523 laboratory-confirmed cases and 135 deaths were reported between Jan. 1 and Oct. 7 of this year. Concern rose that this was caused by some previously unknown factor or even a new strain. However, a collaboration of researchers disproved such a case by analyzing Lassa virus genomes from patient samples. They determined that most patients were still likely receiving the disease from rodent feces or urine.

Lassa fever, which is endemic to West Africa, is often fueled by Mastomys natalensis rodents. They frequent areas in or around humans and their waste tend to be a major point of spread. Human to human transmission of the disease is fairly rare, though possible.

Researchers who worked on the report were from the African Center of Excellence for Genomics of Infectious Diseases at Redeemer’s University; the Broad Institute of MIT and Harvard; the Scripps Research Institute; and Tulane University in New Orleans, among others. It was supported by the National Institute of Allergy and Infectious Diseases (NIAID), the National Human Genome Research Institute (NHGRI), and the NIH Common Fund’s Human Heredity and Health in Africa Program.