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Explained: What is norovirus, the stomach bug that infected two students in Kerala?

Initial reports indicate that two lower primary school students caught the infection through mid-day meals

Norovirus-ExplainedElectron microscopic image of norovirus virions (Source: Centers for Disease Control and Prevention)

At least two cases of norovirus have been found in Thiruvananthapuram among lower primary school students.

Health department officials said the infection, which causes vomiting, diarrhoea and fever as symptoms, was diagnosed after samples were tested at a government analytical lab. More samples have been sent for examination. So far, it is believed that students got food poisoning from mid-day meals distributed at the schools.

What is norovirus?

Norovirus is a highly contagious virus that is also sometimes referred to as the ‘stomach flu’ or the ‘ winter vomiting bug’. It can be transmitted through contaminated food, water, and surfaces. The primary route is oral-faecal.

It is similar to diarrhoea-inducing rotavirus and infects people across age groups. Disease outbreaks typically occur aboard cruise ships, in nursing homes, dormitories, and other closed spaces.

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According to the WHO, emerging evidence suggests that “norovirus infection is associated with intestinal inflammation, malnutrition and may cause long-term morbidity”. It adds that an estimated 685 million cases of norovirus are seen annually, including 200 million cases amongst children under 5

What are the symptoms of norovirus?

The initial symptoms of norovirus are vomiting and/or diarrhoea, which show up one or two days after exposure to the virus.

Patients also feel nauseous, and suffer from abdominal pain, fever, headaches and body aches. In extreme cases, loss of fluids could lead to dehydration.

What precautions can one take?


One may get infected multiple times as the virus has different strains. Norovirus is resistant to many disinfectants and can withstand heat up to 60°C. Therefore, merely steaming food or chlorinating water does not kill the virus. The virus can also survive many common hand sanitisers.

The basic precaution is also the most obvious — repeatedly washing hands with soap after using the lavatory or changing diapers. It is important to wash hands carefully before eating or preparing food. During outbreaks, surfaces must be disinfected with a solution of hypochlorite at 5,000 parts per million.

The US Centre for Disease Control and Prevention suggests that those infected should avoid contact with others and avoid preparing food for others while sick and for two days after symptoms stop.


What is the treatment for norovirus?

The disease is self-limiting. The infection, even though it takes a lot out of the patient, normally lasts only two or three days, and most individuals who are not very young, very old, or malnourished can ride it out with sufficient rest and hydration.

Diagnosis is done by real-time reverse transcription-polymerase chain reaction. No vaccines are available for the disease.

It is important to maintain hydration in the acute phase. In extreme cases, patients have to be administered rehydration fluids intravenously.

First published on: 05-06-2022 at 18:22 IST
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