A norovirus outbreak that never made headlines

First documented outbreak in State in June in Alappuzha reported 950 cases

The recent Norovirus outbreak at the College of Veterinary Sciences in Wayanad hit even national headlines and raised apprehensions that a new infectious pathogen was establishing itself in the State.

It now emerges that the Wayanad outbreak was the second norovirus outbreak in Kerala this year.

The first documented norovirus outbreak in the State was in June in Alappuzha this year. The 950 cases, possibly more, of acute diarrhoeal diseases reported from Alappuzha municipality and nearby panchayats were linked to norovirus.

“Cases of acute gastroenteritis, especially among children, was first clustered in the coastal wards in the municipality and even as we were initiating rapid control measures, it began spreading to nearby panchayats. The outbreak lasted for one-and-a-half months and is the first documented norovirus outbreak in the State,” says S. Shaji, district surveillance officer, who led the investigation.

Self-limiting

Between June 26 and 30, 256 cases of acute gastroenteritis with vomiting and diarrhoea as predominant symptoms were reported. Though the outbreak was spreading rapidly, the disease was self-limiting and over 92% of the patients required just outpatient care

It emerged during the investigation that the outbreak had begun some 10 days after a pipe burst in the Alappuzha municipal area, following which the public water supply had been disrupted. During this period, people were being supplied water from external sources such as RO plants.

Samples of stored drinking water from public supply collected from the house of a patient revealed the presence of coliform bacteria (180/100 ml/mpn), while some samples from the municipal area did not even have the presence of chlorine.

Contamination

In the infected areas, majority of the homes had septic tanks but shockingly, there were also houses without a sanitary latrine or even a pit latrine.

Stool samples collected from patients did not reveal the presence of any bacterial pathogens and were negative for Hepatitis A, rota virus and enteroviruses. Following this 11 stool samples were sent to the field unit of NIV in Alapuzha, RT-q PCR confirmed the presence of norovirus.

The presence of coliform in drinking water samples clearly indicated faecal contamination and noroviruses are spread through the faeco-oral route, through the consumption of contaminated food or water or surfaces contaminated by an infected person.

Previous outbreaks

“We do not know if there have been previous norovirus outbreaks in the State because unless detailed laboratory investigations are conducted into a diarrhoeal outbreak, the virus is not easily identified. It was the rapid pace at which it was spreading and the fact that lab investigations did not only yield any pathogens which led us to a detailed investigation,” Dr. Shaji says.

Even though it was evident that contaminated water was the source of infection, the authorities were unable to pinpoint the source of infection. Meanwhile, the source of infection in the Wayanad outbreak is yet to be found.

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