The Norovirus outbreak: prevention rooted in hygiene

What is the Norovirus and how does it spread? What is the cure for the infection?

November 15, 2021 11:10 am | Updated 06:08 pm IST

Norovirus, Virus, Medical Test, Medical Research, Medical Exam

Norovirus, Virus, Medical Test, Medical Research, Medical Exam

The story so far: Last week, an acute diarrhoeal disease outbreak reported amongst students of the College of Veterinary Sciences at Pookkode, near Vythiri in Wayanad district, was confirmed as Norovirus (NoV) by the authorities. These students were staying in hostels outside the campus and four out of the seven samples sent to the unit of National Institute of Virology, Alapuzha had tested positive for NoV.

Senior health officials later confirmed that the diarrhoeal outbreak had first begun in the second week of October amongst the inmates of the hostel inside the campus. While the illness seemed to subside within two days in the affected persons, the students were sent home by the college authorities as the disease began spreading fast. It was only when the outbreak spread outside the campus that detailed investigations were conducted and NoV was confirmed. Though the outbreak has been contained, the source of the infection has not yet been found.

The first documented NoV outbreak in Kerala was in Alappuzha district this year between June and August when 950 cases of acute diarrhoeal disease, mostly in children, were reported from the municipal area and the nearby panchayats. The outbreak had begun following a pipe burst and water shortage, when water was supplied externally.

What is NoV and how does it spread?

Norovirus is an important cause of acute non-bacterial gastroenteritis in children as well as adults worldwide. The virus was first discovered in connection with an outbreak of acute diarrhoeal disease in Norwalk, Ohio, in 1968 and was called the Norwalk Virus. Later, several stomach flu viruses closely linked to the Norwalk virus were found and together, these are now called Noroviruses. Many stomach flu outbreaks typically in cruise ships have been traced to NoV. The Centers for Disease Control and Prevention (CDC) says over 20 million cases of acute diarrhoeal disease caused by NoV are reported annually in the U.S, a chunk of which are food-borne infections.

According to literature, in one study, in New Delhi, NoV was found to be the second most predominant virus (25.7%) after rotavirus. In southern India, norovirus infection rates of about 10% and 44.4% were reported in two different studies during 2005-06 while a birth cohort study found that about 11.2% of diarrhoeal episodes were attributable to NoV.

Infection is characterised by an acute onset of nausea, vomiting, abdominal cramps, and diarrhoea. The symptoms usually begin 12 to 48 hours after exposure to the infective agent and generally subside within two days.

There is no specific treatment; rest and rehydration with warm fluids should be enough. The disease is self-limiting and rarely dangerous unless severe dehydration is allowed to set in. However, more care is needed if very young children, elderly or pregnant women are infected.

Transmission occurs predominantly by the faecal-oral route, directly or indirectly, through the ingestion of contaminated water or food or surfaces which might have been contaminated when handled carelessly by an infected person or his care-giver.

How are NoV infections prevented?

Prevention is rooted in hygiene. People should wash their hands thoroughly with soap and water before eating and after using the toilet. Fruits and vegetables should be thoroughly washed before eating. Shell fish like oysters, which might have been grown in contaminated waters, should be well-cooked. Boiled and safe drinking water alone should be used.

Infected persons should rest at home and maintain utmost personal hygiene to prevent transmission.

What makes NoV infections a public health concern?

NoV is a highly contagious virus and transmission occurs at a rapid pace because of heavy viral shedding by the infected person.

Even the lowest infectious dose is enough to set off extensive outbreaks, typically in environments such as hostels, schools, hospitals or nursing homes.

Experts also point out that NoV could increasingly become a public health concern because of rapid expansion of the food industry. One infected person in the kitchen or a food handler becoming infected even mildly can take the virus to hundreds of people.

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