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 Table of Contents  
Year : 2017  |  Volume : 61  |  Issue : 4  |  Page : 302-304  

A point source outbreak of acute gastroenteritis among school students in Kerala, India

1 Assistant Professor, Department of Community Medicine, Amrita Institute of Medical Sciences, Kochi, India
2 Technical Consultant, Centre for Public Health Protection, Kollam, Kerala, India
3 General Secretary, Centre for Public Health Protection, Kollam, Kerala, India

Date of Web Publication6-Dec-2017

Correspondence Address:
Rajeswaran Thiagesan
E4/160, Vallalar Street, I Main Road, Otteri Extension, Vandalur, Chennai - 600 048, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijph.IJPH_431_16

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An outbreak investigation was initiated following an outbreak of acute gastroenteritis among schoolchildren in Kottarakara. Steps included active search for cases at schools, describing the outbreak in terms of person, place, and time, generating hypothesis based on the findings from descriptive study, environmental observations, and testing the hypothesis using a case–control design. The final line list consisted of 871 children from different schools who attended a Republic Day parade. Having consumed the lemon juice near railway station (odds ratio [OR] 29.14; 95% confidence interval CI 9.06–93.67) during Republic day parade was associated with the outbreak. The time frame of the disease occurrence, laboratory results, and the results of the analytical study indicated the point source of acute gastroenteritis outbreak as the contaminated water used for lemon juice distributed during the parade. The findings warrant effective food and water safety surveillance, especially during mass gatherings.

Keywords: Acute gastroenteritis, food safety, outbreak investigation, water surveillance

How to cite this article:
Rakesh P S, Thiagesan R, Ramachandran R. A point source outbreak of acute gastroenteritis among school students in Kerala, India. Indian J Public Health 2017;61:302-4

How to cite this URL:
Rakesh P S, Thiagesan R, Ramachandran R. A point source outbreak of acute gastroenteritis among school students in Kerala, India. Indian J Public Health [serial online] 2017 [cited 2022 Nov 27];61:302-4. Available from:

There were at least 32 outbreaks of water/food-borne disease outbreaks reported from Kerala alone in 2016 involving 2421 cases. Many of these outbreaks were due to point sources such as welcome drink distributed during marriage, official ceremonies, juices from hotels, and food distributed during religious rituals and festivals.[1]

Food- and water-borne diseases cause significant morbidity in the general population and are emerging as a growing public health problem. In India, many of the food-borne disease outbreaks go unreported or uninvestigated.

On January 26th night, the taluk headquarters hospital, Kottarakara, Kerala, India, reported an unusual occurrence of acute gastroenteritis among schoolchildren. Cases continued to emerge on subsequent days. By 27th evening, 141 cases were reported to District Surveillance Unit, Integrated Disease Surveillance Project, Kollam.[2] An outbreak investigation was initiated to support the government health system with an objective to describe the epidemiological features of the outbreak including its source.

The huge number of children with similar complaints who sought treatment on 26th and 27th confirmed the existence of an outbreak. Children were from different areas and were studying in different schools. We conducted an initial in-depth interview on January 28 with 15 cases admitted to the hospital. A detailed food history for prior 72 h was taken along with clinical information, personal history, domestic, and school water supply. Apart from that, we met treating clinicians, health workers of the area, school administrators, and a few parents. Predominant symptoms were loose stools, vomiting, and mild abdominal pain which lasted for a day or two. No evidence of severe dehydration or complications was reported. Stool samples sent to district public health laboratory were negative for bacteria on routine testing. Attending a Republic Day parade on January 26 in the town was the only common event identified. None of the other hypothesis-generating interviews led to suspect any other event or factors that could explain the outbreak.

A case definition was framed after discussing with treating clinicians. A probable case of acute gastroenteritis was defined as those with two or more episodes of loose stools or at least one episode of vomiting with or without abdominal pain on or after January 25, 2014. An active search for cases was done by the school health nurses at all schools which participated in the parade. They continuously monitored and updated the line list of students with symptoms.

Attack rates were calculated; a spot map and an epidemic curve were drawn [Figure 1]. Final line list consisted of 871 cases and all of them attended the parade on 26th. Overall attack rate was 58.61% among students who attended the parade. Gender-specific attack rates were 41.28% for boys and 62.35% for girls. Majority of the cases belonged to the age group of 11–14 years (77.1%). Epidemic curve clearly pointed to occurrence of this outbreak as a point source, probably on January 26.
Figure 1: Epidemic curve showing time distribution of cases of acute gastroenteritis.

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Republic Day parade included a procession in the town for around 3 km. A list of all food items distributed during the parade was identified by interviewing affected children and schoolteachers who accompanied them. To get further insights to the source, a case–control study was planned with cases being children from the line list generated. Controls were children who attended the republic day parade but did not develop symptoms. Cases and controls were interviewed by trained school health nurses on January 30 and 31. Of the line list generated, 370 students who were present during these days were interviewed. Questionnaire included demographic details and specific yes/no questions for listed food items consumed during the parade.

Data were analyzed using SPSS 16 (IBM) for Microsoft Windows 7 in Sony VAIO. Chi-square test for any association and OR with CIs was estimated to identify the risk factors associated with the cases. [Table 1] shows the results of the univariate analysis of the case–control study. Having consumed lemon juice distributed near railway station was nearly universal among cases, and the association was found to be statistically significant (OR 87.46 [P< 0.001]).
Table 1: Univariate analysis of factors associated with acute gastroenteritis cases

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The spots from where the food substances were distributed were visited, and samples of water sources used to prepare juices were taken and sent to the laboratory for testing. Since it was a sunny day and the rally started later than usual, schoolchildren were exhausted, which forced them to drink more juices distributed during the day. The volunteers who supplied juice near railway station had to depend on unprocessed water from a nearby well when juices were refilled. Microbiological analysis of the water sample from the well-used to prepare lemon juice had shown heavy growth of  Escherichia More Details coli. The time frame of the disease occurrence, laboratory results, and the results of the analytical study indicated the point source of acute gastroenteritis outbreak as the contaminated water used for lemon juice distributed during the parade. Surveillance was continued in the schools till February 5th. Report was submitted to health authorities and district collector for action.

Diseases related to contamination of drinking water and food constitute a major burden on public health.[3],[4] Systematic reviews of epidemiological evidence from intervention studies, especially outbreak investigations, suggest that drinking-water quality plays an important role in fecal–oral transmission.[5],[6],[7]

The situation warrants effective food and water safety surveillance, especially during mass gatherings. This particular outbreak investigation was an eye-opener to any such future incidences as precautionary and mandatory quality and surveillance measures shall be put in place to avoid any such events. Precautionary activities according to the set standards to prevent food borne outbreaks. The government and its related sectors including health, food safety, water authority, and public together should play an active role in provision and consumption of safe drinking water and food.

For want of laboratory infrastructure, we could not confirm the causative organism of this outbreak. This was a missed opportunity. Case definition would not have picked up mild and subclinical cases. Despite these limitations, the study has many public health implications. An effective food- and water-borne disease surveillance system supported by a strong laboratory network is warranted to combat future food- and water-borne disease outbreaks.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Integrated Disease Surveillance Project. Recently Weekly Outbreak Reports. Available Available from: level=0&linkid=406&lid=3689. [Last accessed on 2016 Dec 04].  Back to cited text no. 1
Government of India. Integrated Disease Surveillance Project. New Delhi: Ministry of Health and Family Welfare. Available Available from: [Last accessed on 2016 Dec 03].  Back to cited text no. 2
Fewtrell L, Colford JM Jr. Water, sanitation and hygiene in developing countries: Interventions and diarrhoea – A review. Water Sci Technol 2005;52:133-42.  Back to cited text no. 3
Clasen T, Roberts I, Rabie T, Schmidt W, Cairncross S. Interventions to improve water quality for preventing diarrhoea. Cochrane Database Syst Rev 2006;19:CD004794.  Back to cited text no. 4
Waddington H, Snilstveit B. Effectiveness and sustainability of water, sanitation, and hygiene interventions in combating diarrhoea. J Dev Eff 2009;1:295-335.  Back to cited text no. 5
Cairncross S, Hunt C, Boisson S, Bostoen K, Curtis V, Fung IC, et al. Water, sanitation and hygiene for the prevention of diarrhoea. Int J Epidemiol 2010;39 Suppl 1:i193-205.  Back to cited text no. 6
Craun GF, Brunkard JM, Yoder JS, Roberts VA, Carpenter J, Wade T, et al. Causes of outbreaks associated with drinking water in the United States from 1971 to 2006. Clin Microbiol Rev 2010;23:507-28.  Back to cited text no. 7


  [Figure 1]

  [Table 1]


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