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Volume 31, Number 8—August 2025

Research Letter

Seroprevalence of Rift Valley and Crimean-Congo Hemorrhagic Fever Viruses, Benin, 2022–2023

Nadine Olk, Anges Yadouleton, Olga Quenum, Stephane Sohou, Aime Goundote, Grace Aho Glele Rodrigue, Blaise Guezo-Mevo, Sonia Bedie, Michael Nagel, Petra Emmerich, Benjamin Hounkpatin, and Jan Felix DrexlerComments to Author 
Author affiliation: Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität of Berlin, Institute of Virology, Berlin, Germany (N. Olk, J.F. Drexler); Ecole Normale Supérieure de Natitingou, Université Nationale des Sciences, Technologies, Ingénierie et Mathématiques, Cotonou, Benin (A. Yadouleton); Laboratoire des Fièvres Hémorragiques Virales, Ministry of Health, Cotonou (A. Yadouleton, O. Quenum, S. Sohou, A. Goundote, G.A.G. Rodrique, B. Guezo-Mevo, S. Bedie, B. Hounkpatin); Deutsche Gesellschaft für Internationale Zusammenarbeit, Bonn, Germany (M. Nagel); Bernhard Nocht Institute of Tropical Medicine, Hamburg, Germany (P. Emmerich); Center of Internal Medicine, University Medicine Rostock, Rostock, Germany (P. Emmerich); German Centre for Infection Research, associated partner Charité-Universitätsmedizin, Berlin (J.F. Drexler)

Main Article

Figure 2

ELISA reactivity for Rift Valley and Crimean-Congo hemorrhagic fever viruses, Benin, 2022–2023. IgG ELISA (ID.Vet, https://bioadvance.life/en/id-vet-2) for RVFV for which a sample/negative percentage <40.0 is considered positive. IgG ELISAs (Euroimmun, https://www.euroimmun.com; Panadea Diagnostics, https://www.panadea-diagnostics.com) for CCHFV for which ratios >1.1 are considered positive according to the manufacturer. A) RVFV competitive ELISA (ID.Vet) using nucleoprotein as antigen. Positive samples, n = 10/650. B) CCHFV indirect ELISA (Euroimmun) using nucleoprotein as antigen. Positive samples, n = 40/650. C) CCHFV immune complex capture ELISA (Panadea) using nucleoprotein as antigen. Positive samples, n = 5/92. D) Reduced indirect IgG ELISA reactivity of CCHFV (Euroimmun) with poly-L-histidine concentrations of 0.01, 0.05, 0.10, 0.50, 1.00, and 2.00 mg/mL. Box plots show sample distribution, displaying medians (thick lines within boxes) and interquartile ranges (box top and bottom edges); whiskers indicate 1.5× interquartile range. Red lines show cutoff levels for ELISAs; gray shading shows the area for borderline results; black triangles show samples positive by RVFV immunofluorescence assay; blue triangles show samples positive by CCHFV immunofluorescence assay. The Spearman correlation was performed in R, and boxplots for RVFV and CCHFV were plotted using the ggplot2 package in R (https://www.r-project.org). Because of the low detection rates of RVFV-specific and CCHFV-specific IgG, negative reverse transcription PCR results, and low serum volumes, we did not perform IgM analyses. CCHFV, Crimean-Congo hemorrhagic fever virus; RVFV, Rift Valley fever virus.

Figure 2. ELISA reactivity for Rift Valley and Crimean-Congo hemorrhagic fever viruses, Benin, 2022–2023. IgG ELISA (ID.Vet, https://bioadvance.life/en/id-vet-2) for RVFV for which a sample/negative percentage <40.0 is considered positive. IgG ELISAs (Euroimmun, https://www.euroimmun.com; Panadea Diagnostics, https://www.panadea-diagnostics.com) for CCHFV for which ratios >1.1 are considered positive according to the manufacturer. A) RVFV competitive ELISA (ID.Vet) using nucleoprotein as antigen. Positive samples, n = 10/650. B) CCHFV indirect ELISA (Euroimmun) using nucleoprotein as antigen. Positive samples, n = 40/650. C) CCHFV immune complex capture ELISA (Panadea) using nucleoprotein as antigen. Positive samples, n = 5/92. D) Reduced indirect IgG ELISA reactivity of CCHFV (Euroimmun) with poly-L-histidine concentrations of 0.01, 0.05, 0.10, 0.50, 1.00, and 2.00 mg/mL. Box plots show sample distribution, displaying medians (thick lines within boxes) and interquartile ranges (box top and bottom edges); whiskers indicate 1.5× interquartile range. Red lines show cutoff levels for ELISAs; gray shading shows the area for borderline results; black triangles show samples positive by RVFV immunofluorescence assay; blue triangles show samples positive by CCHFV immunofluorescence assay. The Spearman correlation was performed in R, and boxplots for RVFV and CCHFV were plotted using the ggplot2 package in R (https://www.r-project.org). Because of the low detection rates of RVFV-specific and CCHFV-specific IgG, negative reverse transcription PCR results, and low serum volumes, we did not perform IgM analyses. CCHFV, Crimean-Congo hemorrhagic fever virus; RVFV, Rift Valley fever virus.

Main Article

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