A spatiotemporal analysis of the spread of African swine fever in Vietnam in 2019.

Introduction: African swine fever (ASF) was first detected in Vietnam in early February 2019 and spread rapidly nationwide. By December 2019, ASF had been reported in 8,509 of 11,055 communes (77%) across all 63 provinces and municipalities. Methods: Descriptive analyses were performed to summarize temporal and spatial patterns of ASF-affected communes (outbreaks). Outbreak data were aggregated weekly (week 1-48) based on onset date, and weekly counts, cumulative numbers, and proportions of affected communes were calculated. To quantify the early spread of ASF, we analyzed commune-level outbreak data from 2019. Temporal progression was assessed using linear and negative binomial regression models, whereas spatiotemporal clusters were identified using a space-time permutation model. Results: The linear regression analysis indicated an approximately 2.5 percentage-point weekly increase in the cumulative proportion of affected communes ( Conclusion: These findings highlight the extensive geographic scale of ASF transmission in Vietnam in the first year of the epidemic. The rapid and extensive spread observed suggests that a stamping-out strategy, as typically implemented, may face substantial challenges under such epidemic conditions. Instead, the results emphasize the importance of impact-mitigation strategies and long-term management approaches, including enhanced biosecurity, farmer support, and measures to maintain a stable pork supply. These findings also provide relevant insights for countries facing similar endemic conditions or at risk of ASF introduction.