Regional Risk Discrepancy Indicates a Slow Outbreak of Infant Botulism, Victoria, Australia

Background: Infant botulism accounts for many new botulism cases each year. Geographic case clustering has been previously described in California. This study aimed to describe whether case clustering was present in Victoria, Australia. Methods: We conducted a retrospective case series of infant botulism presenting to Victorian hospitals between 1978 and 2024. Moran’s I test for spatial autocorrelation was used to determine if spatiotemporal clustering was present. Results: Twelve cases of infant botulism presented to Victorian hospitals in the study period. Using Moran’s I statistic in analyzing the number of cases in each postcode of interest, a case clustering was demonstrated in the northwest of Victoria ( P < 0.01). Conclusions: We describe a geographic case clustering within the relatively sparsely populated northwest in Victoria, Australia.