A Re-Look at Cholera Pandemics from Early Times to Now in the Current Era of Epidemiology

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Cholera affects about three million people annually and kills several thousands. Since 1817 seven cholera pandemics have been described. While the nature of the strains responsible for the first four pandemics are not known, the fifth and sixth pandemics are associated with Vibrio cholerae O1 classical biotype. In the 1960s, V. cholerae El Tor replaced classical strains worldwide, ushering in the seventh pandemic. El Tor cholera is typified with less severe diarrhea, a lower case fatality rate and a higher percentage of asymptomatic cases. Historically, the Indian subcontinent was thought to be the homeland where cholera originated and has been implicated in spreading of the disease. Cholera broke out in Africa and now seems to be continuous and recurrent, leading to high morbidity and mortality in some countries. Current conflicts in the Middle East have been associated with the breakdown of healthcare systems and the emergence of cholera there in a big way. Several discoveries in the past two centuries helped us to understand and manage the disease. Some of the greatest inventions such as rehydration therapy have saved the lives of countless people afflicted with cholera. Whole genome sequencing of V. cholerae and the modern molecular epidemiology of cholera have led to advancements in understanding of the disease and also how the organism has persisted and re-emerged in new areas during the seventh pandemic. Currently, water, sanitation, and hygiene along with the new generation oral cholera vaccines are considered as important interventions and beneficial public health tools in cholera endemic countries and in areas at risk for outbreaks. This review highlights the pandemics that lead to important discoveries and also the new molecular approach in understanding the epidemiology of cholera.