Exposure Incidents and Outcome of Lassa Fever Virus (LASV) Infection among Healthcare Workers in Nigeria, 2019

Background: Outbreaks of respiratory disease, febrile illness and rash occurred in two adjoining rural communities of Imo State, Southeastern, Nigeria, at different times between 2006 and 2020. Laboratory investigation was carried out to determine the aetiological agent of the outbreak. Methodology: Oropharyngeal swabs were collected from 6 individuals showing symptoms of disease, within 3-4 days of appearance of rash. Venous blood samples were also collected from a total of 41 symptomatic persons, their contacts and individuals with resolved infections. Swabs were inoculated into Vero, HEp-2c, B95a and MDCK cell lines. Sera were analyzed using enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G and M to rubella and measles viruses, while immunofluorescence assay was used to detect Lassa fever virus immunoglobulins. Descriptive data were analyzed using the Statistical Package for the Social Sciences (SPSS). Results: Four of the 6 (66.7%) swab samples showed viral activity or cytopathic effect characterized by clumping of cells in Vero cells while 2 (33.3%) in Hep-2c characterized by rounding up of cells. Thirty-nine (95.1%) sera were positive for measles IgG while 13 (31.7%) were positive for IgM. Thirty-six (87.8%) sera were positive for rubella IgG but none was positive for IgM. None of the sera was positive for Lassa fever virus IgG and IgM. Conclusion: Measles virus was responsible for the outbreak among previously vaccinated population in the communities, while Rubella and Lassa fever viruses were excluded as the etiological agents of the outbreak. Keywords: Epidemics; IgG and IgM; Cell lines; Vaccination; Measles virus French title: Épidémie de rougeole dans la population vaccinée du sud-est du Nigéria Contexte: Des flambées de maladies respiratoires, de maladies fébriles et d'éruptions cutanées sont survenues dans deux communautés rurales voisines de l'État d'Imo, dans le sud-est du Nigéria, à des moments différents entre 2006 et 2020. Une enquête en laboratoire a été menée pour déterminer l'agent étiologique de l'épidémie. Méthodologie: Des écouvillons oropharyngés ont été prélevés sur 6 individus présentant des symptômes de maladie, dans les 3 à 4 jours suivant l'apparition de l'éruption cutanée. Des échantillons de sang veineux ont également été prélevés sur un total de 41 personnes symptomatiques, leurs contacts et des personnes souffrant d'infections résolues. Des écouvillons ont été inoculés dans des lignées cellulaires Vero, HEp-2c, B95a et MDCK. Les sérums ont été analysés en utilisant un test immuno-enzymatique (ELISA) pour les immunoglobulines G et M contre les virus de la rubéole et de la rougeole, tandis que le test d'immunofluorescence a été utilisé pour détecter les immunoglobulines du virus de la fièvre de Lassa. Les données descriptives ont été analysées à l'aide du progiciel statistique pour les sciences sociales (SPSS). Résultats: Quatre des 6 échantillons sur écouvillon (66,7%) ont montré une activité virale ou un effet cytopathique caractérisé par l'agglutination des cellules dans les cellules Vero, tandis que 2 (33,3%) dans Hep-2c étaient caractérisés par un arrondissement des cellules. Trente-neuf (95,1%) sérums étaient positifs pour les IgG contre la rougeole tandis que 13 (31,7%) étaient positifs pour les IgM. Trente-six (87,8%) sérums étaient positifs pour les IgG contre la rubéole, mais aucun n'était positif pour les IgM. Aucun des sérums n'était positif pour les IgG et IgM du virus de la fièvre de Lassa. Conclusion: Le virus de la rougeole était responsable de l'épidémie parmi la population précédemment vaccinée dans les communautés, tandis que les virus de la rubéole et de la fièvre de Lassa ont été exclus comme agents étiologiques de l'épidémie. Mots clés: épidémies; IgG et IgM; Lignées cellulaires; Vaccination; Virus de la rougeole

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Boosting understanding of Lassa Fever virus epidemiology: Field testing a novel assay to identify past Lassa Fever virus infection in blood and oral fluids of survivors and unexposed controls in Sierra Leone

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0009255 ◽

2021 ◽

Vol 15 (3) ◽

pp. e0009255

Author(s):

Onome Akpogheneta ◽

Steve Dicks ◽

Donald Grant ◽

Zainab Kanneh ◽

Brima Jusu ◽

...

Keyword(s):

Sierra Leone ◽

Sensitivity And Specificity ◽

Large Scale ◽

Oral Fluid ◽

Field Testing ◽

Lassa Fever ◽

Fever Virus ◽

World Health ◽

Hospitalised Patients ◽

Lassa Fever Virus

Background Despite identification 50 years ago, the true burden of Lassa Fever (LF) across Africa remains undefined for reasons including research focus on hospitalised patients, lack of validated field-feasible tools which reliably identify past infection, and the fact that all assays require blood samples making large-scale surveys difficult. Designated a priority pathogen of epidemic potential requiring urgent research by the World Health Organisation, a better understanding of LF sero-epidemiology is essential to developing and evaluating new interventions including vaccines. We describe the first field testing of a novel species-neutral Double Antigen Binding Assay (DABA) designed to detect antibodies to LF in plasma and oral fluid. Methodology/Principal findings Paired plasma and oral fluid were collected in Sierra Leone from survivors discharged from Kenema Government Hospital Lassa Fever Unit between 1980 and 2018, and from controls recruited in Freetown in 2019. Epidemiological sensitivity and specificity of the DABA measured against historical diagnosis in survivors and self-declared non-exposed controls was 81.7% (95% CI 70.7%– 89.9%) and 83.3% (72.7%- 91.1%) respectively in plasma, and 71.8% (60.0%– 81.9%) and 83.3% (72.7%– 91.1%) respectively in oral fluid. Antibodies were identified in people infected up to 15 years and, in one case, 40 years previously. Participants found oral fluid collection easy and painless with 80% happy to give an oral fluid sample regularly. Conclusions/Significance Given the difficulties of assay validation in a resource-limited setting, including unexpected exposures and diagnostics of varying accuracy, the new assay performed well in both plasma and oral fluid. Sensitivity and specificity are expected to be higher when case/control ascertainment is more definitive and further work is planned to investigate this. Even at the performance levels achieved, the species-neutral DABA has the potential to facilitate the large-scale seroprevalence surveys needed to underpin essential developments in LF control, as well as support zoonotic investigations.

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