Surveillance of Viral Hemorrhagic Fever Viruses in Lassa Fever Suspects in Ondo State, Nigeria

Lassa Fever (LF) continues to be an endemic acute viral hemorrhagic fever (VHF) illness in Nigeria. Many suspected cases of LF infection have subsequently been confirmed negative and raises concerns as to what the diagnosis of such patients could be. Hence this study was to determine the causative agents of unconfirmed LF among initially suspected cases in South Western Nigeria.

In this retrospective study, blood samples originally collected from 233 suspected cases of a LF outbreak response at Owo and Ose LGAs of Ondo State, were transported in triple level packaging and stored at -80°C. All samples were screened for LF IgM and IgG markers and LF PCR. Forty-five out of the stored plasma samples were randomly retrieved and analyzed for presence of IgM for seven other VHF viruses; Chikungunya (CHIK), West Nile (WN), Rift Valley fever (RVF), Yellow fever (YF), Dengue fever (DEN), Zika and Crimean-Congo hemorrhagic fever (CCHF).

Out of 45 samples screened, 1 (2.2%) was positive for YF IgM antibody. The same sample was previously confirmed LF positive by PCR. This LF and YF co-infection was from a male, 23-year old individual.

The presence of co-infections of LF and YF draw to limelight the need to be broad minded in exploring for the presence of other VHF viruses in outbreaks. Further studies are needed to decipher the diagnosis of LF suspected cases.