P-186. Longitudinal Seropositivity of Antibodies Against Arboviruses Among an Agricultural Worker Cohort AGRI in Southwest Guatemala

Abstract Background Zika virus (ZIKV), dengue virus (DENV) and chikungunya virus (CHIKV) are arboviruses transmitted by Aedes mosquitoes. While DENV serotypes 1 and 2 (DENV1 and DENV2) are the most prevalent in Guatemala, serotypes 3 and 4 (DENV3 and DENV4) have caused recent epidemics. In 2024, a public health emergency was declared by the Ministry of Health due to the rise in dengue cases. CHIKV and ZIKV outbreaks were reported between 2014-2017.Evolution of flavivirus serostatus among the AGRI cohort (2020-2022) The graph shows the serologic characteristics of the AGRI cohort against flavivirus infections. A rise in the multytipic DENV serostatus is observed over the years. On the contrary, there is a decline in the flavivirus-naive population.Density distribution of the MFI values against arbovirus-specific antigens The MFI of the antigen-antibody reaction was recorded for each arbovirus. The evolution of cohort-level mean fluorescence intensity (MFI) readings over 3 years is shown. Positivity cutoffs are indicated by the dashed red line. Methods Mean Fluorescence Intensity (MFI) from anti-CHIKV/ZIKV/DENV1-4 antibodies was obtained using an IgG-based multiplex bead assay. Flavivirus-specific beads were coupled with the EDIII protein of ZIKV/DENV1-4. CHIKV beads were coupled with CHIKV E2 protein. We tested 1136 samples from 478 individuals, collected in 2020 (n=478), 2021 (n=338) and 2022 (n=320). A set of 15 samples from children born between 2018-2022 were used as regionally appropriate samples to calculate the positivity cutoffs (mean MFI + 3SD). A previously described algorithm for analyzing flavivirus MFI signals was used to discriminate between naive samples and primary/multitypic infections. Results CHIKV seropositivity was 56.9%, 51.5% and 53.4% for 2020, 2021 and 2022. During the follow up, 12 individuals had a negative-to-positive seroconversion against CHIKV. For 2020, 2021, and 2022, we detected seropositivity for primary infections of DENV1 (16.9%, 9.17%, 10.6%), DENV2 (9.41%, 21.0%, 11.2%), DENV3 (1.88%, 0.30%, 0.00%) and ZIKV (11.9%, 6.51%, 4.38%). Naïve-to-primary seroconversions were found for DENV1 in 2022 (n=12), for DENV2 in 2021 (n=14) and 2022 (n=10), and for ZIKV in 2021 (n=1) and 2022 (n=3). Flavivirus-naive prevalence went from 15.7% in 2020 to 7.8% in 2022. Conclusion Though confirmatory testing is needed, these findings suggest that active DENV1/2, ZIKV and CHIKV transmission was ongoing in the region for this period. Disclosures Blair Weikel, MPH, Merck: Grant/Research Support Molly Lamb, PhD, Merck: Grant/Research Support Daniel Olson, MD, Fundacion para la Salud Integral de los Guatemaltecos: Board Member|Merck: Grant/Research Support|Roche Diagnostics: Grant/Research Support