Investigation of a 2021 Diarrheal Outbreak in a Coastal Sub-district of Bangladesh and Its Seasonal Pattern
DOI:
https://doi.org/10.59096/osir.v19i2.278806Keywords:
diarrhea, outbreak, waterborne disease, Vibrio cholerae, case-control study, BangladeshAbstract
Objectives: Diarrhea is a major health problem in Barisal, a coastal division of southern Bangladesh. In April 2021 a diarrheal outbreak was notified from Barisal health authorities. An investigation team was deployed to describe demographic characteristics and seasonal patterns, identify risk factors of diarrhea in the district, and implement control measures.
Methods: We analyzed seasonality using district health information system for the period 2018–2021 and conducted a matched case-control study in Bakerganj, the most affected sub-district. Cases were residents reporting ≥3 loose watery stools within 24 hours during 18 Apr 2021–1 May 2021. Controls were randomly selected from neighbors of a case without any diarrheal illness. Descriptive statistics were used to summarize demographic characteristics and seasonal trends, and multivariable conditional logistic regression was used to assess associations between potential risk factors and diarrheal illness.
Results: A total of 1,027 diarrheal cases were identified during the outbreak in Bakerganj. Cases increased annually in March (pre-monsoon season) and declined from June (monsoon season). We enrolled 66 cases and 132 matched controls. Drinking untreated surface water (adjusted odds ratio [AOR] 11.6, 95% confidence interval [CI] 2.4–56.3), preparing overnight fermented rice (AOR 2.5, 95% CI 1.1–5.3), and performing ablution (AOR 2.4, 95% CI 1.0–5.9) were significant risk factors. Using surface water treated by aluminum potassium sulfate was protective (AOR 0.3, 95% CI 0.1–0.7). Among stool samples, 27% (20/75) tested positive for Vibrio cholerae by rapid diagnostic test and 29% (11/38) by culture; 5 of 8 surface water samples tested were positive.
Public Health Recommendations: This outbreak occurred before the monsoon and was linked to untreated surface water for drinking and household activities. Public health authorities should implement preventive measures to ensure safe drinking water and distribute sufficient amounts of aluminum potassium sulfate to treat surface water before the annual surge.
References
Das S, Chandra H, Saha UR. District level estimates and mapping of prevalence of diarrhoea among under-five children in Bangladesh by combining survey and census data. PLoS ONE. 2019 Feb 1;14(2):e0211062. doi:10.1371/journal.pone.0211062.
Sin MP, Hasan MZ, Forsberg BC. Change in economic burden of diarrhoea in children under-five in Bangladesh: 2007 vs. 2018. J Glob Health. 2023;13:04089. doi:10.7189/JOGH.13.04089.
Khan AI, Rashid MM, Islam MT, Afrad MH, Salimuzzaman M, Hegde ST, et al. Epidemiology of cholera in Bangladesh: Findings from nationwide hospital-based surveillance, 2014-2018. Clin Infect Dis. 2020;71(7):1635–42. doi:10.1093/cid/ciz1075.
Grant SL, Tamason CC, Hoque BA, Jensen PKM. Drinking cholera: salinity levels and palatability of drinking water in coastal Bangladesh. Trop Med Int Heal. 2015;20(4):455–61. doi:10.1111/tmi.12455.
Chao DL, Roose A, Roh M, Kotloff KL, Proctor JL. The seasonality of diarrheal pathogens: A retrospective study of seven sites over three years. PLoS Negl Trop Dis. 2019 Aug 15;13(8):e0007211. doi:10.1371/journal.pntd.0007211.
Das SK, Begum D, Ahmed S, Ferdous F, Farzana FD. Geographical diversity in seasonality of major diarrhoeal pathogens in Bangladesh observed between 2010 and 2012. 2014;142(12):2530–41. doi:10.1017/S095026881400017X.
Clasen TF, Alexander KT, Sinclair D, Boisson S, Peletz R, Chang HH, et al. Interventions to improve water quality for preventing diarrhoea. Cochrane Database Syst Rev. 2015;2015(10):CD004794. doi:10.1002/14651858.CD004794.
Khanam F, Islam MT, Ahmmed F, Rajib MNH, Hossen MI, Chowdhury F, et al. Evaluation of oral cholera vaccine (Euvichol-plus) effectiveness against Vibrio cholerae in Bangladesh: an interim analysis. BMJ Glob Heal. 2025;10(2):e016571. doi:10.1136/bmjgh-2024-016571.
Conner JG, Teschler JK, Jones CJ, Yildiz FH. Staying alive: Vibrio cholerae's cycle of environmental survival, transmission, and dissemination. Microbiol Spectr. 2016 Apr;4(2):10.1128/microbiolspec.VMBF-0015-2015. doi:10.1128/microbiolspec.VMBF-0015-2015.
World Bank. Bangladesh climate fact sheet [Internet]. Washington (DC): World Bank; 2024 [cited 2025 Jul 29]. <https://www.climatecentre.org/wp-content/uploads/RCCC-Country-profiles-Bangladesh_2024_final.pdf>
World Bank Group. Bangladesh climate risk country profile [Internet]. Washington: World Bank Group; 2021 [cited 2025 Nov 06]. <https://climateknowledgeportal.worldbank.org/sites/default/files/country-profiles/15502-WB_Bangladesh Country Profile-WEB.pdf>
Yan SF, Yu SE, Wu YB, Pan DF, She DL, Ji J. Seasonal variations in groundwater level and salinity in coastal plain of eastern China influenced by climate. J Chem. 2015;2015(1):905190. doi:10.1155/2015/905190.
Abedin MA, Habiba U, Shaw R. Community perception and adaptation to safe drinking water scarcity: salinity, arsenic, and drought risks in coastal Bangladesh. Int J Disaster Risk Sci. 2014;5(2):110–24. doi:10.1007/s13753-014-0021-6.
Hossain MJ, Chowdhury MA, Jahan S, Zzaman RU, Islam SLU. Drinking water insecurity in southwest coastal Bangladesh: how far to SDG 6.1? Water. 2021;13(24):3571. doi:10.3390/w13243571.
Ahmad K, Jahan K, Huq I. Decontamination of drinking water by alum for the preparation of oral rehydration solution. Food Nutr Bull. 1984;6(2). doi:10.1177/156482658400600214
Kabir R, Khan HTA, Ball E, Caldwell K. Climate change impact: the experience of the coastal areas of Bangladesh affected by cyclones Sidr and Aila. J Environ Public Health. 2016;2016:9654753. doi:10.1155/2016/9654753.
Kraay ANM, Man O, Levy MC, Levy K, Ionides E, Eisenberg JNS. Understanding the impact of rainfall on diarrhea: testing the concentration-dilution hypothesis using a systematic review and meta-analysis. Environ Health Perspect. 2020;128(12):126001. doi:10.1289/EHP6181.
Viegelmann GC, Dorji J, Guo X, Lim HY. Approach to diarrhoeal disorders in children. Singapore Med J. 2021;62(12):623–9. doi:10.11622/smedj.2021234.
Breslow NE, Day NE. Statistical methods in cancer research. Volume II--the design and analysis of cohort studies. IARC Sci Publ. 1987;(82):1–406.
Tamanna R, Hossain I. Household vulnerability in drinking water and diarrheal disease among children in coastal villages. J Prev Soc Med. 2025;43(1):27–32. doi:10.3329/jopsom.v43i1.82422.
Laboratory Services, International Centre for Diarrhoeal Disease Research, Bangladesh. Vibrio cholerae (water sample) [Internet]. Dhaka: International Centre for Diarrhoeal Disease Research, Bangladesh; [cited 2021 Sep 18]. <http://labservices.icddrb.org/test-details/355>
Das SK, Begum D, Ahmed S, Ferdous F, Farzana FD, Chisti MJ, et al. Geographical diversity in seasonality of major diarrhoeal pathogens in Bangladesh observed between 2010 and 2012. Epidemiol Infect. 2014;142(12):2530–41. doi:10.1017/S095026881400017X.
Amin MA, Tauheed I, Ahsan MA, Khan ZH, Islam MT, Akhtar M, et al. Exploring climate links and clinical association of the diarrheal disease using data from an upsurge in Dhaka, Bangladesh: a cross-sectional study. Heal Sci Reports. 2025;8(12):e71641. doi:10.1002/hsr2.7
Singleton FL, Attwell R, Jangi S, Colwell RR. Effects of temperature and salinity on Vibrio cholerae growth. Appl Environ Microbiol. 1982;44(5):1047–58. doi:10.1128/aem.44.5.1047-1058.1982.
Daboul J, Weghorst L, DeAngelis C, Plecha SC, Saul-McBeth J, Matson JS. Characterization of Vibrio cholerae isolates from freshwater sources in northwest Ohio. PLoS One. 20203;15(9):e0238438. doi:10.1371/journal.pone.0238438.
Sarker AR, Sultana M, Mahumud RA, Ali N, Huda TM, Salim uzzaman M, et al. Economic costs of hospitalized diarrheal disease in Bangladesh: a societal perspective. Glob Heal Res Policy. 2018 Jan 5:3:1. doi:10.1186/s41256-017-0056-5.
Chowdhury F, Khan IA, Patel S, Siddiq AU, Saha NC, Khan AI, et al. Diarrheal illness and healthcare seeking behavior among a population at high risk for diarrhea in Dhaka, Bangladesh. PLoS One. 2015;10(6):e0130105. doi:10.1371/journal.pone.0130105.
Sarker AR, Sultana M, Mahumud RA, Ali N, Huda TM, Salim uzzaman M, et al. Economic costs of hospitalized diarrheal disease in Bangladesh: a societal perspective. Glob Heal Res Policy. 2018;3(1). doi:10.1186/s41256-017-0056-5.
Hasan SMT, Das S, Faruque ASG, Khan AI, Clemens JD, Ahmed T. Taking care of a diarrhea epidemic in an urban hospital in bangladesh: Appraisal of putative causes, presentation, management, and deaths averted. PLoS Negl Trop Dis. 2021;15(11):e0009953. doi:10.1371/journal.pntd.0009953.
Chowdhury F, Khan AI, Harris JB, Larocque RC, Chowdhury MI, Ryan ET, et al. A comparison of clinical and immunologic features in children and older patients hospitalized with severe cholera in Bangladesh. Pediatr Infect Dis J. 2008;27(11):986–92. doi:10.1097/INF.0b013e3181783adf.
Zaman K, Ryun Kim D, Ali M, Ahmmed F, Im J, Islam MT, et al. Can cholera ‘hotspots’ be converted to cholera ‘coldspots’ in cholera endemic countries? The Matlab, Bangladesh experience. Int J Infect Dis. 2020;95:28–31. doi:10.1016/j.ijid.2020.02.055.
Longini IM, Nizam A, Ali M, Yunus M, Shenvi N, Clemens JD. Controlling endemic cholera with oral vaccines. PLoS Med. 2007;4(11):e336. doi:10.1371/journal.pmed.0040336.
Khan AI, Islam T. Outbreak of diarrheal diseases causes mortality in different geographical locations of Bangladesh during the 2021 COVID-19 era. Front Public Health. 2023;11:1103518. doi:10.3389/fpubh.2023.1103518.
Alam M. Vibrio cholerae transmits through water among the household contacts of cholera patients in cholera endemic coastal villages of Bangladesh, 2015-2016 (CHoBI7 Trial). Front Public Health. 2018;6:238. doi:10.3389/fpubh.2018.00238.
van Halem D, Olivero S, de Vet WWJM, Verberk JQJC, Amy GL, van Dijk JC. Subsurface iron and arsenic removal for shallow tube well drinking water supply in rural Bangladesh. Water Res. 2010;44(19):5761–9. doi:10.1016/j.watres.2010.05.049.
Dhanasekar P, Rajayyan JS, Veerabadiran Y, Kumar KS, Kumar KS, Chinnadurai N. Evaluation of alum and purification process of water by coagulation method. Bull Pioneer Res Med Clin Sci. 2022;1(1):24–9. doi:10.51847/R8GyfOmMDh.
Unahlekhaka A, Mehta G. The tsunami disaster in Asia. Int J Infect Control. 2006;2(1). doi:10.3396/ijic.v2i1.3925.
Akanda AS, Jutla AS, Gute DM, Sack RB, Alam M, Huq A, et al. Population vulnerability to biannual cholera outbreaks and associated macro-scale drivers in the Bengal Delta. Am J Trop Med Hyg. 2013;89(5):950–9. doi:10.4269/ajtmh.12-0492.
Khanam F, Islam T, Bhuiyan R, Hossen I, Rajib NH, Haque S, et al. The Enterics for Global Health (EFGH) Shigella surveillance study in Bangladesh. Open Forum Infect Dis. 2024;11(Suppl 1):S76–83. doi:10.1093/ofid/ofad653.
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2026 Outbreak, Surveillance, Investigation & Response (OSIR) Journal
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
