REALISE: A two-year study tracking Lassa fever seroprevalence and contributing risk factors in Guinea’s Gueckedou region

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Introduction Lassa virus (LASV), the cause of Lassa fever (LF), is endemic in Guinea. Although the detection of acute LF cases is rising in the country, data on LASV seroprevalence at the community level remain limited. The REALISE study aims to address this gap by assessing LASV seroprevalence and associated risk factors across four sites in the Gueckedou region, with active engagement of local communities. Methods A 2-year longitudinal study (2021-2023) involved 500 participants from three rural and one urban sites, which were selected based on previous laboratory surveillance data from the region. Community engagement began six months prior to sampling. Blood samples and questionnaires were collected at study start (T0), 12 months (T2), 18 months (T3), and 24 months (T4). Serological tests (PANADEA Diagnostics) for immunoglobulin G (IgG) and M (IgM) against LASV nucleoprotein (NP) were performed. IgM-positivity indicated recent infection, and real-time RT-PCR (altona Diagnostics) was done on these samples. Results Of the 500 participants enrolled at T0, 13% were lost to follow-up at T4. At T0, anti-NP IgG prevalence was of 83.4% in rural areas in contrast to 63.2% in urban areas. At T4, anti-NP IgG increased in both rural and urban areas to 88.5% and 64.9%, respectively. Anti-NP IgM ranged from 0.3% to 1.7% across all sites and follow up time points. All RT-PCR tests on IgM positive samples were negative, and no participant reported illness. Analyses are currently ongoing to explore LF risk factors. Conclusion Participants from rural areas exhibit the highest LASV seroprevalence rates as compared to those from urban areas, likely due to rodent reservoirs presence. Seroconversions indicate ongoing exposure and highlight the need for further research on LF. Our findings promote community-centered research and support the global Lassa vaccine strategy

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