Noroviruses – also known as winter vomiting bugs - can be described as a group of viruses that causes serious gastroenteritis illness in humans and some animals. Also referred to as small round structured viruses or Norwalk-like viruses, this virus can cause a person to develop a rapid onset of sickness, diarrhoea, nausea, vomiting, and occasionally abdominal pain as well– all symptoms associated with gastroenteritis.
First discovered by Dr J. Zahorsky in 1929 who classified it as inter vomiting disease, this disease is extremely contagious and can easily spread from one person to another. It's also termed as Norwalk virus because it was the cause behind an outbreak of gastroenteritis in an elementary school in Norwalk, Ohio in 1968. However, since that epidemic, scientists have concluded that there are several viruses which closely resemble the virus found in Norwalk. Which is why besides the Norwalk virus, Toronto virus, Bristol Virus, Snow Mountain, Hawaii viruses along with 150 other similar viruses causing similar symptoms are all classified as noroviruses.
As per data released by the CDC (Centre for Disease Control and Prevention, this virus is responsible for causing 685 million cases of acute gastroenteritis thus making it the leading cause of acute gastroenteritis across the globe. As a matter of fact, nearly 90 percent of all non-bacterial outbreaks of gastroenteritis have been linked to noroviruses worldwide. In addition, nearly 200 million of those cases include children under 5 which directly results in the deaths of an estimated 50,000 children annually. That said, the norovirus can affect people of all ages and it’s possible to to be affected with the illness several times over the course of a lifetime.
While noroviruses outbreaks are more common during winter months or cooler climates, they can strike any time of the year. That said, nearly half of the reported cases have been observed in the period between December – February in countries located above the equator. In countries situated below the equator, the majority of the incidences have been reported in the period between June – August. As per the Health Protection Agency (HPA), it has been reported that 130 – 250 norovirus outbreaks are reported annually in the UK while affecting between 600,000 and a million people in the UK every year.
It needs to be mentioned that a norovirus infection shouldn't be mistaken for the stomach flu. It's also referred to as the cruise ship virus because several incidences of this virus outbreaks have been reported on cruise ships. Currently, norovirus holds the disreputable distinction of being among the leading causes of food-borne disease and deaths across the world.
Norovirus can be easily transmitted from person to person. Any consumption of contaminated food or contact with a surface or material contaminated with fluid or faeces of an infected person can cause norovirus infection.
In an infected individual, the norovirus tends to attack and attach itself to the cells lining the gastrointestinal tract. Thereon the virus proceeds to infect the cells causing the infected person’s gastrointestinal tract to stop processing fluids properly resulting in diarrhoea and vomiting.
The reason why norovirus is extremely contagious and spreads with ease is because it can be present in the infected individual’s faeces even before they start feeling sick, and can stay for two weeks or longer even after they have started feeling better. Coupled with the fact that most people don’t practice basic hygiene which increases the potential of the virus spreading easily from person to person.
Make no mistake of it, norovirus is a serious illness that can make an individual extremely ill while seriously affecting children and the elderly in particular. It’s easy to get infected with norovirus as people affected with the norovirus illness shed millions of virus particles which can spread under the following circumstances:
Norovirus usually spread quickly in closed places or crowded communities such as day-cares, overnight camps, nursing homes or other long-term care facilities, schools, dorms, prisons, and cruise ships. Further, there are certain types of foods, in particular, which can easily get contaminated and thereon, commonly involved in outbreaks which include:
That being said, any food served raw or handled by an infected person even after being cooked is likely to get contaminated. Besides, noroviruses can also be carried and transmitted to humans by other animals such as dogs. Which is why certain norovirus infections are considered to be a zoonotic disease i.e. a disease which has been transferred between animals and humans.
It has been observed that symptoms usually start manifesting itself between 12 to 48 hours in a person after being exposed to the norovirus and can last anywhere from one to three days. In most cases, healthy individuals affected with norovirus illness tend to get better within 1 to 3 days. Most people affected with norovirus exhibit the following symptoms:
Children and the elderly can even suffer from severe dehydration and showcase symptoms such as:
Children under the age of 12 who display these symptoms should seek immediate medical advice as there could be a risk of a serious medical issue. It also needs to be mentioned that in certain individuals who have been previously exposed to norovirus, there might be no symptoms at all as it has appeared that they have formed some sort of immunity or resistance to the virus. There’s also an additional subset of people who are immune to the virus irrespective of the fact that they have previously exposed to the virus or not. As of now, there’s no plausible explanation behind why certain people are unaffected by the virus.
The primary reason why outbreaks are so common when it comes to norovirus is owing to the nature of the virus. The norovirus as stated before is highly contagious in nature which increases their likelihood of sweeping across mass populations. Not only can they be easily transmitted through the air – making someone who breathes the air immediately infected – but they can also be spread via direct contact. Moreover, the virus has the ability to survive unscathed in an environment for several days. To add to that, since there are several types of norovirus strains, and immunity is compromised almost immediately in case of susceptible people; makes controlling the spread of these diseases more difficult.
In most cases, outbreaks of norovirus illness are a result of infected people spreading the virus to others through various forms of direct contact, including either caring for them in caregiving facility or preparing or sharing food/liquids and/or eating utensils/objects with them. These factors increase the risk of outbreaks in large public facilities such as hospitals, schools, prisons, restaurants, cruise ships as such places tend to be populated by a high number of humans at any given point of time. As a matter of fact, more than half of all norovirus outbreaks reported in the United States are said to occur in long-term care facilities.
Restaurants are another hotspot where outbreaks are prone which is further highlighted by the fact that nearly 50 percent of all outbreaks caused due to food-related illness is as a result of the deadly norovirus. Infected employees who are in direct contact with the food can easily spread the virus to customers or fellow staff through served food, close proximity with other staff members/customers, etc. In case of schools and cruise ships, because of the nature of the structure where people often share dining areas and rooms, an outbreak is likely because infected people might touch objects/surfaces thus making it easier for the norovirus to spread.
According to the CDC, there have also been reports of waterborne outbreaks as a result of sewage contamination of wells and recreational water in community places. Furthermore, oysters in waters, salad dressings, cake icings, and cold food products contaminated by the norovirus have also been associated with outbreaks.
When it comes to the Norovirus, there is no specific group who’s more at risk. Anyone and everyone can contract this infection. Similarly, it can affect individuals of all ages. The young and elderly, in particular, are at a higher risk of getting infected – since dehydration is more common in these age groups. Which why they need to take extra precaution to stay safe. Here’s a list of the potential risk factors that can play a role in increasing a person's likelihood of becoming infected with the norovirus:
Once an individual is infected with a norovirus, they usually become temporarily immune against the disease – which usually doesn’t last for more than 14 weeks.
While the Norovirus as such is not lethal in most people, certain people who are at higher risk need to take adequate precaution as the resultant symptoms could produce dire complication in case they are not carefully treated and quickly addressed. Some of the complications arising out of norovirus are described as under:
Most individuals infected with the norovirus have nothing to fear as the symptoms go away on their own within 2-3 days or once the body has been adequately rehydrated. However, help should be immediately sought if the symptoms persist longer especially vomiting and diarrhoea occurring due to dehydration.
Before the advent of rapid diagnostic techniques, stool, vomit, and environmental swabs of infected individuals were analysed using specialist devices such as electron microscopes, serum antibody increases, and ELISA. However, these tests were deemed less effective and sensitive in detecting the norovirus genetic material. The RT-PCR test (reverse transcriptase-polymerase chain reaction) is a new and advanced technique which has been developed and is currently being used in several clinical diagnostic and monitoring tests. Unlike the previous methods, the RT-PCR test is able to churn out definitive results while allowing for precise quantification of the samples – all within just a matter of a few minutes as well.
It’s important to test outbreaks for norovirus as regular testings’ can rule out incidences of other diseases such as rotavirus, Vibrio, Escherichia, and other organisms which showcase similar symptoms.
It needs to be mentioned that treating or preventing infection from norovirus is not possible because there is currently no vaccine or drug available. Moreover, antibiotics will prove to be ineffective in fighting the virus as antibiotics fight against bacteria, not viruses.
In the majority of the cases, treatment is not required as infections tend to resolve by themselves without causing any long-term complications. However, in cases of dehydration, increasing the fluid intake has been recommended to ease out the vomiting and diarrhoea caused by dehydration. Sometimes medications might also be administered to help relieve patients of severe nausea and vomiting, In the case of severely dehydrated patients, intravenous fluids (IV) packed with electrolytes (promethazine [Phenergan], prochlorperazine [Compazine], or ondansetron [Zofran]) might be recommended.
The best treatment is to immediately inform your healthcare professional and getting the symptoms checked out. Medications might be given to manage the symptoms (especially dehydration). Patients will be recommended to take plenty of rest and stay home to recover. Food high in sugar or fat along with carbonated (fizzy) drinks or undiluted juice should be avoided at all costs. In the case of children and elderly, a bland diet comprising of rice, bread, bananas, applesauce, pasta, and clear fluids is recommended.
Preventing norovirus can be achieved by practising basic hygiene at all times. Here are some ways individuals can lower their risk of contracting infections.