Serological Investigation of Laboratory-Confirmed and Suspected Ebola Virus Disease Patients During the Late Phase of the Ebola Outbreak in Sierra Leone
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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.
KeywordsEbola virus (EBOV) Late phase Serologic investigation IgM IgG
Hundreds of Chinese and Sierra Leonean staff on-site participated in specimen collection, transportation, detection, and data analysis. We especially acknowledge the excellent work of six previous detection teams of China CDC (mobile and fixed lab) and indispensable support (materials and reagents) of the National Institute for Viral Disease Control and Prevention, China CDC. We also express our deep condolences to Dr. Abdul Kamara of the Ministry of Health and Sanitation, Sierra Leone who contributed a lot to this project but passed on after the successful control of Ebola epidemic in Sierra Leone. We also appreciate Dr. Zheng Xing and Dr. Feng Liu for the useful comments of this manuscript. This study was supported by National Mega project for Infectious Disease, Ministry of Science and technology (Grant Nos. 2016ZX10004222-002, 2016ZX10004222-003), National Natural Science Foundation of China (Grant Nos. 81373141 and 81401312) and National key project of Ebola research, National Natural Science Foundation of China (NSFC, Grant No. 81590763).
M Liang, JL, DL, GW, FG, AK, M Lebby, and BK designed the study, YL, WW, YS, Xianda Yang, AL, CL, QS, SC, DS, HH, ZZ, Xiuxu Yang, IK, SK, GB, AT, and JL prepared the reagents, assessed the specimens, and acquired the data. YL, M Liang, JL, and DL analyzed the data. YL, SZ, AL, JL, and M Liang wrote and edited the manuscript.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
Animal and Human Rights Statement
This study did not involve human experimentation, and all the blood samples were collected from Ebola patients with prior consent of the Ministry of Health and Sanitation of Sierra Leone. Biosafety evaluations were approved by the National Institute for Viral Disease Control and Prevention, China CDC. All experimental operations were handled following the Standard Operational Protocol approved by China CDC.
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