Jaundice Outbreak in a Single-Village Cluster
In a subdistrict of 18,000 people, the medical officer reports 48 cases of acute jaundice over 21 days, all from one village of 1,200 residents. Thirty-one are men and 17 are women, aged 16-44 years. Eight are pregnant women, two of whom have delivered stillborn infants. Most patients had 3-5 days of fever, malaise, anorexia, and nausea before jaundice. The village gets water from a single borewell that supplies a standpipe; a sewage line runs within 3 metres of the borewell and is intermittently under pressure. There is no chlorination. The panchayat reports that the pump was repaired 4 weeks ago and has run continuously since. Stool and serum samples from 6 patients have been sent to the district laboratory; results are pending. The district has no recorded outbreak of jaundice in the past 5 years. A community health worker has started advising boiling of water.
1. Construct a working case definition for this outbreak and explain how you would confirm that it is an outbreak.
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A useful clinical case definition is: acute onset of jaundice with dark urine and at least two of fever, anorexia, nausea, vomiting, or right upper quadrant discomfort, in a resident of the village between the dates of the cluster. A confirmed case requires IgM anti-hepatitis A or IgM anti-hepatitis E, or detection of hepatitis E RNA; a probable case is a clinically compatible illness epidemiologically linked to a confirmed case or to the implicated water source. The case definition should be simple, sensitive, and applied consistently by the investigating team. To confirm an outbreak, compare the 48 cases in 21 days with the expected baseline, which is effectively zero because no jaundice outbreak has been recorded in 5 years. Calculate the attack rate: 48 divided by 1,200, or 4%. Build a line list with age, sex, date of onset, water exposure, and pregnancy status; plot an epidemic curve and a spot map. Verify the diagnosis with laboratory testing and exclude alternative causes such as drug-induced liver injury, leptospirosis, malaria, dengue, and biliary obstruction. A cluster alone is not proof; the epidemiological and laboratory links must fit.
2. State the most likely hypothesis and outline the investigation you would do to test it.
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The most likely hypothesis is faecal-oral transmission of hepatitis E from sewage-contaminated borewell water. The single water source, the nearby sewage line under pressure, the lack of chlorination, the recent pump repair, and the high mortality among pregnant women all fit hepatitis E. To test this, conduct a retrospective cohort or case-control study among village residents. Interview cases and non-cases about which water source they used, whether they boiled water, and exposure to other sources. Collect water samples from the borewell and standpipe for coliform counts, chlorine residual, turbidity, and, if available, hepatitis E RNA. Inspect the borewell casing, the sewage line, and the surrounding drainage. Test serum from cases for IgM anti-HEV and stool for HEV RNA; test household contacts to identify asymptomatic infection. Calculate attack rates by water source and by boiling practice. Map cases by date and location to see whether the epidemic curve fits a point source or continuing common-source exposure. The investigation should proceed while control measures are already underway.
3. What immediate control measures would you advise, and how would you protect pregnant women?
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Stop using the borewell immediately and provide safe water through boiling, chlorination, or tanker supply. Repair the sewage leak and inspect the borewell casing; superchlorinate the water source and verify chlorine residual and coliform counts before reuse. Advise all residents to boil water until the supply is proven safe. Intensify surveillance with daily reporting, active house-to-house case finding, and a line list. Health education should cover hand hygiene, safe water, and safe food handling. Notify the district health authorities under the integrated disease surveillance system. Pregnant women need special protection because hepatitis E mortality can reach 20-25% in pregnancy. Identify all pregnant women in the village, advise them to use only boiled or chlorinated water, refer them for antenatal monitoring, and arrange early referral to a higher centre if jaundice or symptoms develop. Immunoglobulin is not recommended for routine post-exposure prophylaxis. The two stillbirths should be investigated and reported. Control measures must be monitored with repeat water testing and case counts.