A screening of the DNA of Lassa fever virus has shown the virus responsible for this year’s outbreak is no different from others but is unable to explain why the current outbreak is larger than others.
In only two months, more than 300 people contracted Lassa fever, surpassing the entire the total number of cases throughout 2017.
Researchers at Irrua Specialist Teaching Hospital, Edo State, in collaboration with partners from Germany-based Bernhard-Nocht Institute for Tropical Medicine deployed real-time sequencing of the DNA of Lassa fever virus to help respond to the ongoing epidemic.
They analysed the genetic makeup of Lassa virus taken from the blood of seven patients from Edo, Ondo, Ebonyi and Imo and compared them to 83 DNA sequences obtained during previous years from across Nigeria.
The sequencing found no new virus lineages, meaning “that the circulating viruses appear to be very similar to the viruses from previous years,” the Nigeria Centre for Disease Control said.
It also indicates Lassa fever cases were mostly caused by viruses that are not “epidemiologically linked,” said NCDC chief executive Chikwe Ihekweazu.
The viruses circulating in the 2018 outbreak appear to originate from virus lineages and strains known to be circulating in Nigeria.
The analysis also showed the most likely route of transmission continues to be spill over of viruses from the rodent reservoir to humans rather than extensive human-to-human transmission.
“The most important question being investigated at the moment is what has caused an outbreak of this magnitude, at this time?” said Ihekweazu.
“One of the possible answers to this question is the emergence of a new Lassa virus lineage or strain with increased virulence or transmissibility. Evidence from this work, although limited to seven viruses at the moment suggests that this is unlikely to be the case.”
More than 110 people have been killed. At least 1,800 people who may have had contact with people infected are under watch across the country.