Spatiotemporal Dynamics and Trend Analysis of African Swine Fever Virus in Romanian Wild Boar Populations (2018–2024)

Abstract

Background: African Swine Fever (ASF) remains a critical threat to the swine industry globally, with wild boars (Sus scrofa) acting as a major wildlife reservoir. Romania has been one of the most severely affected European countries since the virus’s introduction. Objectives: This study aims to estimate the long-term spatiotemporal trends, environmental persistence, and transmission dynamics of ASF virus (ASFV) in the Romanian wild boar population based on a finalized dataset of 1443 confirmed cases distributed across an 80-month timeline (May 2018–December 2024). Methods: Advanced epidemiological workflows integrating spatial and temporal modeling frameworks were developed. Spatiotemporal cluster detection was performed using SatScan to identify significant disease hotspots. Generalized Additive Models (GAMs) were utilized to model non-linear seasonal trends and spatial patterns of carcass persistence. Furthermore, the time-varying reproduction number (Rt) was calculated using a Bayesian renewal framework via the EpiEstim package, parameterized with a wild boar serial distribution (mean = 10.3 days; SD = 4.2 days). Results: SatScan identified one most primary cluster in Dobrogea and five other major recurrent hot spots in Muntenia, Transylvania, and Moldova. The GAM analysis revealed a strong, statistically significant seasonal pattern, with case detection from carcasses peaking markedly during the winter months when low temperatures favor environmental virus stability. The Bayesian Rt reconstruction disclosed three distinct epidemiological phases: a sharp initial invasion peak at a mean Rt of 2.38 (95% Crl: 1.82–3.02), followed by regional wave-like oscillations, and a distinct long-term stabilization in the late endemic phase, hovering dynamically around a stationary mean of 1.01 (95% Crl: 0.87–1.16). Conclusions: Our findings statistically validate the shift from an acute epidemic wave to a self-sustaining, chronic endemic equilibrium within the natural habitat, driven by constant carcass-mediated environmental re-seeding. These insights underscore that successful disease mitigation must prioritize the rapid, targeted removal of infected carcasses in high-risk forest matrices rather than generic population reduction strategies.