Underreporting or Failed Notification? Global Botulism Reporting, 2000-2022

Botulism is a rare, potentially fatal illness caused by botulinum toxins produced by Clostridium bacteria. There are no coordinated worldwide reporting mechanisms for botulism cases and therefore few reliable case frequency estimates. This study aimed to establish an international benchmark for case frequency to determine estimated global rates of underreporting of botulism cases. To this end, a comprehensive, multilingual search of major global and national databases, including gray data and government sources, was performed. Data from case series were pooled, standardized against United Nations midyear population estimates, and analyzed using Kolmogorov-Smirnov tests to identify normally distributed data series. National incidence rates of normally distributed series were compared with that of the United States, which was considered the gold standard due to its extensive data reported for 2004-2018. A total of 6,932 botulism cases from 59 nations were identified in the literature, with a global case fatality rate of 1.37%. The national mean incidence rate ranged from 0.00 to 8.04 cases per million people, with an international mean incidence rate of 0.62 cases per million people. At the continent level, incidence rates tended toward normal distributions, although few countries outside of North America and Europe exhibited normal distributions. Based on comparisons with the US standard, an estimated 88.71% of botulism cases worldwide were unreported in 2016. Better awareness of botulism among healthcare professionals, coordinated global reporting mechanisms, and research on additional contributing factors to underreporting would enable better understanding of global case frequency, thereby potentially reducing the global incidence of botulism and improving outcomes.