O37: one of the exceptions that prove the rule.

Between 1965 and 1968, outbreaks of cholera in Sudan and former Czechoslovakia provoked considerable public health concern. These still represent important historical events that need to be linked to the growing genomic evidence describing the aetiological agent of cholera, . Whilst O1 serogroup are canonically associated with epidemic and pandemic cholera, these events were caused by a clone of toxigenic O37 that may be more globally distributed than just to Europe and North Africa. Understanding the biology of these non-O1 strains of is key to understanding how diseases like cholera continue to be globally important. In this article, we consolidate epidemiological, molecular and genomic descriptions of the bacteria responsible for these outbreaks. We attempt to resolve discrepancies in order to summarize the history and provenance of as many commonly used serogroup O37 strains as possible. Finally, we highlight the potential for whole-genome sequencing of O37 isolates from strain collections to shed light on the open questions that we identify.