Background: Indian subcontinent being an important region in the fight to eliminate cholera needs better cholera surveillance. Current methods miss most infections, skewing disease burden estimates. Triangulating serosurvey data, clinical cases, and risk factors could reveal India's true cholera risk.

Methods: We synthesized data from a nationally representative serosurvey, outbreak reports and risk factors like water, sanitation and the Multidimensional Poverty Index, to create a composite vulnerability index for assessing state-wise cholera risk in India. We tested 7,882 stored sera samples collected during 2017-18 from individuals aged 9-45 years, for vibriocidal antibodies to Vibrio cholerae O1 using a cut-off titre ≥320 defining as elevated titre. We also extracted data from the 2015-19 Integrated Disease Surveillance Programme and published cholera reports.

Results: Overall, 11.7% (CI: 10.4-13.3%) of the sampled population had an elevated titre of cholera vibriocidal antibodies (≥320). The Southern region experienced the highest incidence (16.8%, CI: 12.1-22.8), followed by the West (13.2%, CI: 10.0-17.3) and North (10.7%, CI: 9.3-12.3). Proportion of samples with an elevated vibriocidal titre (≥320) was significantly higher among individuals aged 18-45 years (13.0% CI: 11.2-15.1) compared to children 9-17 years (8.6%, CI 7.3-10.0, p<0.05); we found no differences between sex or urbanicity. Between 2015-2019, the Integrated Disease Surveillance Program (IDSP) reported 29,400 cases of cholera across the country. Using the composite vulnerability index, we found Karnataka, Madhya Pradesh, and West Bengal were the most vulnerable states in India in terms of risk of cholera.

Conclusion: The present study showed that cholera infection is present in all five regions across India. The states with high cholera vulnerability could be prioritized for targeted prevention interventions.