Serosurveillance of viral pathogens circulating in West Africa

Abstract

BackgroundSub-Saharan Africa is home to a variety of pathogens, but disease surveillance and the healthcare infrastructure necessary for proper management and control are severely limited. Lassa virus, the cause of Lassa fever, a severe hemorrhagic fever in humans is endemic in West Africa. In Sierra Leone at the Kenema Government Hospital Lassa Diagnostic Laboratory, up to 70 % of acute patient samples suspected of Lassa fever test negative for Lassa virus infection. This large amount of acute undiagnosed febrile illness can be attributed in part to an array of hemorrhagic fever and arthropod-borne viruses causing disease that goes undetected and untreated.MethodsTo better define the nature and extent of viral pathogens infecting the Sierra Leonean population, we developed a multiplexed MAGPIX® assay to detect IgG antibodies against Lassa, Ebola, Marburg, Rift Valley fever, and Crimean-Congo hemorrhagic fever viruses as well as pan-assays for flaviviruses and alphaviruses. This assay was used to survey 675 human serum samples submitted to the Lassa Diagnostic Laboratory between 2007 and 2014.ResultsIn the study population, 50.2 % were positive for Lassa virus, 5.2 % for Ebola virus, 10.7 % for Marburg virus, 1.8 % for Rift Valley fever virus, 2.0 % for Crimean-Congo hemorrhagic fever virus, 52.9 % for flaviviruses and 55.8 % for alphaviruses.ConclusionsThese data exemplify the importance of disease surveillance and differential diagnosis for viral diseases in Sierra Leone. We demonstrate the endemic nature of some of these viral pathogens in the region and suggest that unrecognized outbreaks of viral infection have occurred.

Vaccine platforms for the prevention of Lassa fever

“…In these rodents, the virus exhibits persistent, asymptomatic infection. Due to their ubiquitous geographic distribution across the West African region, the population-at-risk for Lassa fever is estimated at nearly 60 million people [3,4,7]. LASV fever cases are typically the result of rodent-tohuman transmission events, facilitated by contact with infectious rodent urine or faeces in the household environment [2].…”

“…Lassa fever is endemic to several West African countries. Sierra-Leone, Liberia, Guinea, and Nigeria are most heavily affected; however, LASV infections have also been detected throughout the Côte d'Ivoire, Togo, Benin, Ghana, Central African Republic, Democratic Republic of Congo, Senegal, and southern Mali [4][5][6][7]. As a nonspecific febrile illness with a high proportion of asymptomatic cases, LASV infection is often unreported or misdiagnosed, precluding accurate determination of its true burden.…”

Laboratory Diagnosis of Lassa Fever

“…This assay has lower limits of detection for Lassa virus nucleoprotein and IgM than traditional ELISAs (53). The same group also developed and tested a multiplex MAGPIX IgG assay for a wide spectrum of hemorrhagic fever viruses, including alphaviruses, arenaviruses, flaviviruses, and filoviruses (14). Further development of multiplex MAGPIX assays, including testing for Lassa virus antigen and common endemic diseases such as malaria, would assist with the diagnosis and clinical management of suspected Lassa fever cases, especially in scenarios of coinfection with Lassa virus and bacterial or parasitic organisms where multiple therapeutic modalities may be indicated.…”

“…While the detection of a new positive IgG titer combined with an IgM response in the correct clinical setting may support a diagnosis of Lassa fever, the detection of a positive IgG response alone is insufficient to make a diagnosis. Lassa IgG titers may persist for decades (64), and seroprevalence studies in regions of endemicity have shown 4 to 55% of healthy individuals living in areas where the virus is endemic have detectable Lassa virus IgG titers (14,52,55,65,66).…”

Annual Incidence of Lassa Virus Infection in Southern Mali

“…1 The impact of LASV on the public health resources in these countries is significant with an estimated 10-30% of adult hospital admissions and 14% of all febrile disease attributed to LASV infection. [2][3][4] Recent ecological studies conducted in response to the identification of sporadic cases of Lassa fever in other west African countries including Benin, Togo, Ghana, Cote d'Ivoire, and Mali suggest a larger region where LASV is circulating. [5][6][7][8][9][10][11] As a result, it is likely that the overall burden of LASV infection across west Africa is underestimated.…”