LASV emergence per host: human versus rodent
Here, we seek to phylogenetically infer ancestry and descent between LASV sequences detected in rodents and humans in selected localities within West Africa in order to provide increased insight into virus transmission at the rodent-human boundary.
Our aim is to compile a dataset including LASV sequences collected from both humans and Mastomys rodents within distinctive hotspots of Lassa fever.
In a first study we phylogenetically compared LASV sequences obtained in two localities: Ekpoma in Nigeria and Kenema in Sierra Leone. We performed a time-calibrated phylogeny, using a Bayesian analysis on 198 taxa including 102 sequences from rodents and 96 from humans. Contrary to expectation, our results show that LASV strains detected in humans within these localities, even those sampled recently, are consistently ancient to those circulating in rodents in the same area.
Therefore, our results may suggest the occurrence of human-to-rodent transmission (reverse zoonosis).