Seroepidemiological surveillance of neutralizing antibodies against dengue virus serotypes among healthy adults in Bangkok, Thailand

Bangkok is a hyper-endemic urban area for dengue virus (DENV), where ongoing transmission poses a significant public health risk. Comprehensively understanding the interplay between human immunity, vector ecology, and environmental determinants is essential for developing effective, sustainable dengue control strategies. Population-level immunity provides insights into prior dengue exposure, and the presence of neutralizing antibody may reflect protection against infection. While most previous studies have focused on children, serological data on adults, who constitute the majority of those with continuous exposure, remain limited. This study aimed to characterize neutralizing antibody responses to all four DENV serotypes among healthy adults residing in Bangkok. Residual serum samples from 198 healthy adults collected in 2022 were analyzed, with equal distribution of males and females across five age groups. Neutralizing antibody responses against parental DENV-1 to DENV-4 were assessed using the focus reduction neutralization test (FRNT), with seropositivity defined as an FRNT₉₀ titer ≥10 to ensure assay specificity. Overall, 77.3 %; 95 % CI: 70.9–82.6 of individuals were seropositive for at least one DENV serotype. The lowest seroprevalence rate (54.2 %; 95 % CI: 40.3–67.4) was observed in the youngest (21–30 years) age group. Higher neutralizing antibody titers (FRNT₉₀ 100–1000) were more frequently detected against DENV-1 (51/114, 44.7 %; 95 % CI: 35.9–53.9), and DENV-2 (50/125, 40 %; 95 % CI: 31.8–48.8). These findings indicate age-related differences in DENV seropositivity and suggest recent or ongoing circulation of DENV-1 and DENV-2. The results underscore the importance of continued serotype-specific surveillance and support the implementation of an integrated One Health approach to dengue prevention in endemic urban settings.