Probably one of the biggest outbreaks of this century that has shaken parents and children across continents. The “winter vomiting bug”, as it is popularly known, is not possibly country specific and could strike anywhere. Would it strike elsewhere too?
But what causes the spread of this virus? The schools? the people? the children?
While schools are plagued by cases of absenteeism caused by vomiting among students, what few institutions know and understand are the major causes of such illnesses, and how they can be prevented at the institutional level. Dr Mrigank Warrier takes up the discussion with fellow doctors to profile one such lesser known, but leading cause of vomiting and diarrhoea among children — The Norovirus.
Hark back to your school days. You will surely remember missing a few days of school because of ‘loose motions’, and your parents justifying your absence to your teachers by writing in your school diary/calendar: ‘Was suffering from an upset stomach’. If you are a parent yourself, you have no doubt performed this task for your own child when he or she fell sick.
Diarrhoea and/or vomiting are among the most common causes of school absenteeism. They are the symptoms of a group of illnesses that are clustered by doctors under a common heading: acute gastroenteritis (AGE) — short-term spells of these symptoms that are caused by infections of the digestive tract. From bacteria and fungi to parasites and even stress, AGE has a variety of causes; among the least known are viruses.
It would not be an exaggeration to say that thousands upon thousands of viruses can cause AGE; many are similar to each other and difficult to distinguish. They cannot be differentiated based on symptoms.
Despite the availability of advanced diagnostic tests, they are also notoriously difficult to identify. Since the treatment is often the same for all (no antibiotics, only regular hydration), doctors usually don’t bother trying to zero down on which particular virus caused the illness.
However, it is important to note that there are a few viruses responsible for a majority of the cases. Rotavirus is the leading culprit; but a growing, immensely successful immunisation program under which a vaccine against it is administered to all children, has curbed the havoc wreaked by rotavirus. Which is why it is time to turn our attention to the second most important cause — against which there is no vaccine and hence no protection — noroviruses.
Norovirus and school-children
An international study that analysed almost 2,000 cases of childhood diarrhoea found that 11.2% of them were associated with norovirus. A Peruvian study revealed that a whopping 71% of all children up to the age of two years have suffered from a norovirus-associated AGE.
The numbers from India are alarming too. Of 226 stool samples collected from children with AGE in Delhi, 36 revealed noroviruses. About 44% of all suspected cases of non-bacterial AGE in Chennai were found to be caused by norovirus. Another study in Pune, Aurangabad and Nagpur revealed that 55% of all norovirus-associated AGE victims suffered from very severe disease. About 15% of all children hospitalised in Christian Medical College, Vellore for diarrhoea were shedding norovirus.
According to the National Institute of Virology (Pune), norovirus infects 7.5% of all children at least once. The number of cases peaks in winter, because of which it is known as the ‘wintervomiting disease’. In western India, a study revealed spikes in cases during the summer months too.
How do noroviruses spread?
The symptoms of norovirusassociated AGE are diarrhoea, nausea, vomiting, low-grade fever and abdominal cramps. Virus particles are shed in the stools, and to a lesser extent in the vomit of patients. Hence, by coming in contact with contaminated surfaces like toilet seats which transfers the virus from hands to the mouth, and by eating food or drinking water handled by people with improper hand hygiene, norovirus is spread from person to person. Recurrent infections are extremely common.
The disaster of norovirus outbreaks
Not only is the virus potent, it is also shed by kids before they even begin to exhibit symptoms; this continues long after the child is asymptomatic. Hence, even an apparently healthy child, or one who seems to have recovered from his illness, is a potential source of infection.
Parents of children who are infected are advised to keep their child home from school for 2-3 days even after the symptoms disappear. In an increasingly competitive, overloaded education system where teachers struggle to complete teaching the syllabus, and multiple exams and extracurricular activities are scheduled throughout the week, this advisory is unlikely to be heeded. On the flip side, missing an entire week of school can upset a child’s life.
Elderly people are also extremely susceptible to norovirus. In the US, norovirus cases are most frequently seen in old-age homes. Noroviruses are also responsible for a majority of diarrhoea outbreaks in healthcare settings. Cruise ships on long voyages are an isolated environment where improper hygiene by a single food-handler can infect an entire ship, as is often reported by the western media.
How to prevent the spread of norovirus
The US Center for Disease Control advocates the following methods:
• Wash hands with soap and warm running water for a minimum of 20 seconds before and after contact with patients, after using the lavatory, and/ or before and after eating. Alcohol-based hand sanitisers alone won’t do.
• Wash your fruits and vegetables. Cook seafood thoroughly.
• If you’re sick, don’t cook or care for others for at least 2 to 3 days after you recover.
• Clean contaminated surfaces first, then disinfect them. Use a chlorine bleach solution with a concentration of 1,000 to 5,000 ppm (5 to 25 tablespoons of household bleach (5.25%) per gallon of water) or other disinfectant registered as effective against norovirus by the Environmental Protection Agency. In areas with high levels of soiling and resistant surfaces, up to 5000 ppm chlorine bleach may be used.
• Clean carpets with detergent and warm water, and follow this with steam cleaning.
• Steam-clean all soft furnishings that may be damaged by bleach
• Discard all disposable cloths in biohazard bags
• Launder all non-disposable cloths, i.e. linens, blankets, towels, and clothing
What’s the catch?
Chlorine-based disinfectants are among the most effective virucidal disinfectants. However, noroviruses are relatively resistant to hypochlorite. Some strains of the virus have been found to require ≥500 ppm of hypochlorite to achieve statistically significant reduction in virus concentration. Noroviruses are also resistant to inactivation using quaternary ammonium compound formulations at all concentrations.
A majority of food-borne norovirus illnesses is a result of contamination by infected food-handlers during preparation. Ready-to-eat foods, and foods handled after cooking are the most frequently identified products associated with outbreaks. The virus cannot be completely degraded despite heating to 72 degrees, and can persist on the surface of refrigerated foods for at least 10 days, and in mineral and tap water for over two months.
With home-cooked food sent in tiffin boxes being increasingly replaced by catering provided by facility management companies in schools, it is critical that the latter employ a combination of regular disinfection and use of personal protective equipment by foodhandlers to prevent a potential outbreak that is always on the horizon. Schools need to support them by teaching and supervising proper hand-washing done by each and every student; then, and only then, will schools become the safe, healthy temples of education they are intended to be.