Ahead of Print -Undiagnosed Acute Viral Febrile Illnesses, Sierra Leone - Volume 20, Number 7—July 2014 - Emerging Infectious Disease journal - CDC
Volume 20, Number 7—July 2014
Undiagnosed Acute Viral Febrile Illnesses, Sierra Leone
Author affiliations: US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, USA (R.J. Schoepp, C.A. Rossi); Kenema Government Hospital, Kenema, Sierra Leone (S.H. Khan, A. Goba); Metabiota, San Francisco, California, USA (J.N. Fair)
The West African country of Sierra Leone is located in a Lassa fever–hyperendemic region that also includes Guinea and Liberia. The causative agent of Lassa fever is Lassa virus (LASV), a member of the Arenaviridae family. Lassa fever is a severe, often fatal, hemorrhagic illness; the virus causes 100,000–300,000 infections and 5,000 deaths each year in the region (1).
In 2002, Sierra Leone emerged from a brutal 11-year civil war that left the country with little infrastructure and much of its formal economy destroyed. Today Sierra Leone is undergoing substantial economic growth; however, poverty, unemployment, and inadequate health care remain major challenges. Through the Mano River Union–Lassa Fever Network, a variety of organizations are building diagnostic capacity for Lassa fever that will lead to better understanding of the disease and its treatment (2–5). These scientific efforts are centered in eastern Sierra Leone at the Kenema Government Hospital (Kenema, Sierra Leone) within the Lassa fever–hyperendemic region (Figure). The Lassa Fever Ward, a 16-bed facility on the hospital grounds, is dedicated to treating patients suspected of having Lassa fever and is supported by the Lassa Diagnostic Laboratory.
Each year, suspected Lassa fever infections result in submission of ≈500–700 samples to the Kenema Government Hospital Lassa Diagnostic Laboratory (J. Bangura, unpub. data). Samples come from throughout the Lassa fever–hyperendemic region and initially are screened for malaria by thick blood smear and, if negative, are tested for LASV. LASV infection is determined by the presence of virus detected by an antigen-detection ELISA and by the presence of IgM determined by using an IgM-capture ELISA. Generally only 30%–40% of samples tested are positive for LASV antigen and/or LASV-specific IgM; therefore, 60%–70% of patients have acute diseases of unknown origin. We investigated what other arthropod-borne and hemorrhagic fever viral diseases might be causing serious illness in the region and confounding the diagnosis of Lassa fever. We tested samples from these patients using IgM-capture ELISAs to virus pathogens that could occur in the region and mimic Lassa fever. We tested for IgM to dengue virus (DENV), West Nile virus (WNV), yellow fever virus (YFV), Rift Valley fever virus (RVFV), chikungunya virus (CHIKV), Ebola virus (EBOV), Marburg virus (MBGV), and Crimean-Congo hemorrhagic fever virus (CCHFV). Follow up analyses included IgG ELISAs and/or confirmatory plaque-reduction neutralization tests (PRNTs). This study provides a better understanding of the differential diagnoses for Lassa fever in the region, which can lead to improved diagnostic capability and disease treatment.
Dr Schoepp serves as chief of the Applied Diagnostics Department, Diagnostic Systems Division, US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, USA. His research interests include the pathogenesis and ecology of arthropod-borne and hemorrhagic fever viruses in the human host and the animal and/or arthropod reservoir.
We thank all the dedicated and hardworking employees of the Kenema Government Hospital. We extend special thanks to Bayon Bockarie, Mohammed Fullah, James J. Bangura, Ashley M. Zovanyi, Tamara E. Clements, Denise K. Danner, Jim F. Barth, Matthew A. Voorhees, and Eric M. Mucker for their expert technical assistance. We also acknowledge Robert F. Garry for his generosity in sharing the valuable clinical samples analyzed in this study.
The laboratory work was funded in part by the Division of Global Emerging Infections Surveillance and Response System Operations at the Armed Forces Health Surveillance Center, Research Plans (C0169_10_RD, C0410_11_RD, and C0602_12_RD), through USAMRIID and by the US Department of Defense Cooperative Biological Engagement Program, through Metabiota, Inc., San Francisco, CA, USA.
- Figure. Lassa fever–hyperendemic region (white area) comprising Guinea, Sierra Leone, and Liberia in West AfricaInsert, upper right: Africa, with West African countries highlighted; lower left: Lassa Diagnostic Laboratory, Kenema Government Hospital,...
- Table 1. Case definition used to detect suspected Lassa fever at Kenema Government Hospital, Kenema, Sierra Leone, October 2006–October 2008
- Table 2. Patients’ antibody reactions to arthropod-borne and hemorrhagic fever virus antigens, Lassa Diagnostic Laboratory, Kenema, Sierra Leone, October 2006–October 2008
- Table 3. Results of Immunologic assays for serum samples that tested IgM positive only for alphaviruses, Lassa Diagnostic Laboratory, Kenema, Sierra Leone, October 2006–October 2008
- Table 4. Results of immunologic assays for serum samples testing IgM positive only for ebolaviruses, Lassa Diagnostic Laboratory, Kenema, Sierra Leone, October 2006–October 2008
Suggested citation for this article: Schoepp RJ, Rossi CA, Khan SH, Goba A, Fair JN. Undiagnosed acute viral febrile illnesses, Sierra Leone. Emerg Infect Dis [Internet]. 2014 Jul [date cited].http://dx.doi.org/10.3201/eid2007.131265