Prof. Noam Barda

Objective West Nile virus (WNV) is a mosquito-borne pathogen of growing public health concern that is endemic in Israel and has been responsible for intermittent outbreaks. The seroprevalence and durability of functional antibody responses in asymptomatic WNV-infected populations remain unclear. Methods We screened a large cohort of asymptomatic healthcare workers (HCWs) for WNV IgG and neutralizing antibody titers. Predictors of seropositivity and neutralization levels were assessed using multivariable regression. Among seropositive individuals, longitudinal samples, collected up to 44 months prior to the final blood sampling, were analyzed to evaluate neutralizing antibody kinetics. Results Of 2365 HCWs screened (median age 47 years; 66.6% females), 14.8% (n = 301) were WNV IgG seropositive, and 94.0% of these demonstrated detectable neutralizing efficacy. Age was independently associated with IgG seropositivity (adjusted OR 1.33 per 10 years; 95% CI: 1.23-1.45). Neutralizing efficacy was high (Geometric-Mean-Titer 6171, 95% CI: 4361-8723), and IgG and neutralizing antibody titers were correlated (R² = 0.17). Over 44 months, a 23% annual decrease in neutralizing titers was observed. Conclusion WNV seropositivity increases with age, indicating cumulative exposure. Correlation between IgG and neutralizing efficacy suggests durable protection among seropositive individuals. Despite waning antibody levels, high neutralizing capacity likely confers extended protection.