Serological Investigation of Laboratory-Confirmed and Suspected Ebola Virus Disease Patients During the Late Phase of the Ebola Outbreak in Sierra Leone

This study aimed to investigate the serological characteristics of Ebola virus(EBOV) infection during the late phase of the Ebola outbreak in Sierra Leone. In total, 877 blood samples from 694 suspected Ebola virus disease(EVD) cases assessed from March to December 2015, were analyzed via real-time reverse transcription polymerase chain reaction(RT-PCR) for viral RNA and enzyme-linked immunosorbent assay(ELISA) and Luminex to detect antibodies against EBOV. Viral load and EBOV-specific IgM/IgG titers displayed a declining trend during March to December 2015. Viral RNA load decreased rapidly at earlier stages after disease onset, while EBOV-specific IgM and IgG still persisted in 58.1%(18/31) and 93.5%(29/31) of the confirmed EVD patients and in 3.8%(25/663) and 17.8%(118/663) of the RNA-negative suspected patients in the later phase, respectively. Dynamic analysis of longitudinally collected samples from eight EVD patients revealed typically reversed trends of declining viral load and increasing IgM and/or IgG titers in response to the EBOV infection.The present results indicate that certain populations of Sierra Leone developed immunity to an EBOV infection in the late phase of the outbreak, providing novel insights into the risk assessment of EBOV infections among human populations.

Intra-host Ebola viral adaption during human infection

The onsite next generation sequencing(NGS)of Ebola virus(EBOV)genomes during the 2013–2016 Ebola epidemic in Western Africa provides an opportunity to trace the origin,transmission,and evolution of this virus.Herein,we have diagnosed a cohort of EBOV patients in Sierra Leone in 2015,during the late phase of the outbreak.The surviving EBOV patients had a recovery process characterized by decreasing viremia,fever,and biochemical parameters.EBOV genomes sequenced through the longitudinal blood samples of these patients showed dynamic intra-host substitutions of the virus during acute infection,including the previously described short stretches of 13 serial TNC mutations.Remarkably,within individual patients,samples collected during the early phase of infection possessed Ts at these nucleotide sites,whereas they were replaced by Cs in samples collected in the later phase,suggesting that these short stretches of TNC mutations could emerge independently.In addition,up to a total of 35 nucleotide sites spanning the EBOV genome were mutated coincidently.Our study showed the dynamic intra-host adaptation of EBOV during patient recovery and gave more insight into the complex EBOV-host interactions.

HIV prevalence in suspected Ebola cases during the 2014-2016 Ebola epidemic in Sierra Leone

Background:The 2014-2016 Ebola virus epidemic in West Africa was the largest outbreak of Ebola virus disease(EVD)in history.Clarifying the influence of other prevalent diseases such as human immunodeficiency virus infection and acquired immune deficiency syndrome(HIV/AIDS)will help improve treatment and supportive care of patients with EVD.Case presentation:We examined HIV and hepatitis C virus(HCV)antibody prevalence among suspected EVD cases from the Sierra Leone-China Friendship Biological Safety Laboratory during the epidemic in Sierra Leone.HIV and HCV antibodies were tested in 678 EVD-negative samples by enzyme-linked immunosorbent assay.A high HIV prevalence(17.6%)and low HCV prevalence(0.22%)were observed among the suspected cases.Notably,we found decreased HIV positive rates among the suspected cases over the course of the epidemic.This suggests a potentially beneficial effect of an improved public health system after assistance from the World Health Organization and other international aid organizations.Conclusions:This EVD epidemic had a considerable impact on the public health system and influenced the prevalence of HIV found among suspected cases in Sierra Leone,but also provided an opportunity to establish a better surveillance network for infectious diseases.