Kerala's Health Department on January 23, 2023 confirmed two positive cases of Norovirus in Ernakulam district, as per a post on the Facebook page of the District Medical Health Office, Ernakulam on January 23, 2023. As many as 62 students and some of their parents developed symptoms of the virus, following which two samples were sent for testing, news reports said. (find news reports here, here and here)

Norovirus is a highly contagious viral illness that causes gastroenteritis — inflammation of the stomach and intestines which lead to vomiting and diarrhoea. Globally, an estimated 685 million cases of norovirus are detected annually, with over one third of the cases in children under five years.

Sudden outbreaks occur when infected persons spread the virus through direct contact in a closed community like a long term care facility or a school, said Dr Rajeev Jayadevan, Senior Consultant Gastroenterologist and Co-Chairman of the Indian Medical Association's National COVID-19 Task Force. He explained that the disease can spread through contaminated food and water and can also be transmitted through the faeces or vomit of infected people.

Norovirus: Symptoms and Treatment

"It's extremely easy for this virus to enter a person's body as it only takes a few virus particles to cause symptoms such as diarrhoea, vomiting, dehydration, nausea, stomach pain, fever and body ache," said Dr Jayadevan.

Since there is no vaccine for this virus, treatment mainly involves rehydrating an infected person. "There is no antiviral agent. ORS (Oral Rehydration Solution) is key because an infected person loses electrolytes in the body," said Dr Jayadevan. "One need not buy expensive brands of ORS either. To make it, take a litre of boiled water, six teaspoons of sugar and half teaspoon of salt. Further, people need not flock to the hospital because the majority of cases can be handled at home."Also, alcohol-based sanitisers are of no use for decontamination, he said. While SARS-CoV-2 (the virus that causes Covid-19) has a lipid layer, norovirus contains a protein layer which cannot be destroyed by an alcohol sanitiser. Hence surfaces can only be decontaminated with a bleach solution, he added.

Since norovirus is a viral infection, antibiotics cannot treat it, said Dr Jayadevan. Instead, he advised infected persons to stay at home until they recover, wash hands with soap before a meal and especially after using the toilet, drink only boiled water and clean surfaces using a bleach solution.

One of the main reasons why it's challenging to contain the spread of norovirus is because there are many types of noroviruses. This means that a person may contract the illness multiple times and may not have the immunity to fight against a specific type of norovirus. While it is possible to develop immunity to specific types, it is not known exactly how long immunity lasts, as per the CDC.

How dangerous is the norovirus?

Kerala had reported an outbreak of around 65 cases in 2021 (54 from Wayanad and 11 from Alappuzha), as per a Rajya Sabha response given by Bharati Pravin Pawar Minister of State in the Ministry of Health and Family Welfare on December 7, 2022.

A 2016 study published in the National Library of Medicine, studied the norovirus disease, re-infection rates, strain prevalence and genetic susceptibility to noroviruses in a birth cohort of 373 Indian children for three years. Of 1,856 diarroheal episodes, 207 (11.2%) were associated with the norovirus while 20.4% of vomiting-only episodes were positive for the norovirus.

Globally, the virus causes an estimated 200,000 deaths per year (0.02% of the cases), including 50,000 deaths among children, mainly affecting low-income countries. The virus has very low mortality if diagnosed and treated well, said Dr Jayadevan. But, he added, neglecting the symptoms and ignorance about the disease can lead to complications, especially among vulnerable groups such as older individuals and young children.

"Diarrhoea and vomiting lead to dehydration and loss of electrolytes. This can lead to renal shutdown and complications and electrolyte imbalance can lead to excessive loss of potassium in the body. However, these are seen only in severe cases," Dr Jayadevan concluded.