An Outbreak of Ebola Virus Disease in the Lassa Fever Zone

Abstract

Background: Kenema Government Hospital (KGH) has developed an advanced clinical and laboratory research capacity to manage the threat of Lassa fever, a viral hemorrhagic fever (VHF). The 2013-2016 Ebola virus (EBOV) disease (EVD) outbreak is the first to have occurred in an area close to a facility with established clinical and laboratory capacity for study of VHFs.

Methods: Because of its proximity to the epicenter of the EVD outbreak, which began in Guinea in March 2014, the KGH Lassa fever Team mobilized to establish EBOV surveillance and diagnostic capabilities.

Results: Augustine Goba, director of the KGH Lassa laboratory, diagnosed the first documented case of EVD in Sierra Leone, on 25 May 2014. Thereafter, KGH received and cared for numbers of patients with EVD that quickly overwhelmed the capacity for safe management. Numerous healthcare workers contracted and lost their lives to EVD. The vast majority of subsequent EVD cases in West Africa can be traced back to a single transmission chain that includes this first diagnosed case.

Conclusions: Responding to the challenges of confronting 2 hemorrhagic fever viruses will require continued investments in the development of countermeasures (vaccines, therapeutic agents, and diagnostic assays), infrastructure, and human resources.

Keywords: Ebola virus; Lassa virus; West African Ebola outbreak 2013–16; epidemiology; genomic sequencing; research capacity building; viral hemorrhagic fever diagnostics.

Figure 1.

Key events during the development of the Lassa fever program at Kenema Government Hospital and important locations of the 2013–2016 West African Ebola outbreak. A, Time line of major Lassa fever research programs and initiatives at Kenema Government Hospital prior to the emergence of Ebola virus (EBOV) disease in West Africa. B, Map of area where Sierra Leone, Guinea, and Liberia converge. The 2013–2016 EBOV variant is named after the Makona (Moa) river, which forms parts of the Guinea–Sierra Leone and Guinea-Liberia borders [8]. Abbreviations: CDC, Centers for Disease Control and Prevention; ELISA, enzyme-linked immunosorbent assay.

Figure 2.

Diagnosis of the first case of Ebola virus (EBOV) disease (EVD) and changes in caseload and case numbers over time. A, Time line of events at Kenema Government Hospital (KGH) following the introduction of EBOV into Sierra Leone. Images from left to right are a colorized version of a electron micrograph of EBOV, taken by F. Murphy (Centers for Disease Control and Prevention); (2) a photograph of a team from the Viral Hemorrhagic Fever Consortium (VHFC; from left to right, Simbirie Jalloh [program manager], Mambu Momoh [laboratory technician], Dr S. Humarr Khan [director, Lassa fever program], Dr Kristian Andersen [then in the laboratory of Pardis Sabeti at Harvard/Broad and currently at the Scripps Research Institute], and Stephen Gire [then in the laboratory of Pardis Sabeti and currently at NextGen Jane) assists in establishing diagnostic capability for EBOV at KGH following the declaration of an EVD outbreak in nearby Guinea; cropped photograph of healer [17]. B, Diagnosis of first EVD case in Sierra Leone by Augustine Goba on 25 March 2014. An asterisk indicates the location of the 122–base pair positive band, using a VHFC-designed polymerase chain reaction assay (performed by K. Andersen, using KGH primers) [14]. Other primers include the Baize et al [3] modification of the Filo A/B [15] primer set for EBOV detection (285–base pair control band; white square, negative for sample) and the Ölschläger et al [4] modification of the Demby et al primer set [5] for Lassa virus (LASV) detection (318–base pair control band; white circle, negative for sample). There is 1 mismatch in the forward primer and 1 mismatch in the reverse primer, compared with the EM095 sequence (accession number KM034550) [14], which may explain why the modified FiloA/B primer set failed to amplify this sequence. EM095 is also referred to as case 2. Case 1 presented to KGH on 23 March 2014 but received a diagnosed of EVD after case 2 tested positive. C, Cumulative numbers of EVD cases admitted to KGH from 25 May to 18 June 2014. These cases were the basis of the genomic sequencing article by Gire et al [14] and the clinical study by Schieffelin et al [16]. D, Numbers of EVD cases diagnosed per month in Kenema District and in Sierra Leone between 25 May 2014 and 17 February 2016.

Figure 3.

Transmission chains involving the early cases of Ebola virus disease (EVD) as the disease spread into Sierra Leone. Details of the transmission chains are provided in Table 1 and the text. Abbreviation: Dx, diagnosed.

Figure 4.

Possible reemergence of Ebola virus (EBOV) disease in eastern Sierra Leone and fortification of Kenema Government Hospital (KGH) for managing viral hemorrhagic fevers (VHFs). A, Distribution of the Gola Forest across West Africa. Location of Kenema town on the edge of the forested area suggests that the area is at risk for reemergence of EBOV. The box with dotted lines is the area in which EBOV emerged in the 2013–2016 outbreak. The inset shows a billboard posted on the main road into Kenema reading, “Welcome to Kenema: Gateway to the Gola Rainforest National Park.” B, Existing and planned infrastructure to manage VHFs at KGH. The satellite image of the KGH complex is from Google Maps. The figure was inspired by a presentation by Jason Moses (IGLU, London, United Kingdom), who designed the new VHF ward. A 44-bed VHF clinical ward to replace the historic 14-bed Lassa ward will be completed in 2016 through funding by the Naval Engineering Facilities Command. The facility will feature high-efficiency solar power generation, LED lighting, ensured water supply, enhanced infection control, and improved decontamination facilities and waste disposal. The KGH laboratory is equipped for diagnosis of VHFs (via rapid diagnostic tests, enzyme-linked immunosorbent assays, and quantitative polymerase chain reaction analyses) and for performing clinical chemistry analyses, hematological assays, flow cytometry, and cell culture. Establishment of genomic sequencing capacity is expected during the first quarter of 2017. A ruggedized liquid nitrogen generator and cryostorage tanks were delivered in January 2016, A biorepository is expected to be operational in the second quarter of 2016.