An outbreak of acute neurological illness associated with drinking water source following a cyclone in Eluru, West Godavari district, Andhra December 2020

Background: In December 2020, over 500 residents of Eluru City were hospitalised with seizures and sudden loss of consciousness (LOC) resembling the neurotoxic effects of organochlorine poisoning after a flooding event during the last week of November 2020. We described the epidemiological investigation of outbreak and identified risk factors. Methods: We performed descriptive analysis followed by 1:1 unmatched case-control study. Cases were identified through house-to-house search and review of medical records at district hospital. A case defined as sudden onset LOC or new-onset seizures in an Eluru resident aged >= 1 year, December 1-15, 2020 and a control as absence of neurological symptoms in a person aged >= 1 year selected randomly from same administrative division of the case. We compared cases and controls for possible risk factors and calculated adjusted odds ratio (aOR) with 95% confidence interval (CI). Biological and environmental samples were tested for contaminants. Results: We identified 545 cases (56% males), including one death. Seizures were reported in 491 (90%) cases. Median age was 27 years (interquartile range: 17-37 years) and 480 (88%) cases resided in urban area. Cases were clustered in administrative divisions supplied by municipal water reservoirs. Cases were more likely than controls to use municipal water as primary source of drinking water (aOR = 4.6, 95% CI = 1.6-13.0). High levels (average: 14.6 mg/l) of organochlorine compounds were detected in all municipal water samples (acceptable limit: <0.001 mg/l). Conclusion: This investigation highlights water ingestion as an exposure pathway for environmental contami-nants (organochlorines) in the community after largescale flooding. We recommended strengthening safe water surveillance in natural disaster response contingency plans in Eluru.