Introduction

Norovirus is a group of contagious viruses that is the leading cause of acute gastroenteritis (stomach flu, which inflames the stomach lining and intestines) around the world. Also known as the “winter vomiting bug” due to a higher rate of outbreaks in the colder season, scientists in the UK have estimated that 3 million cases occur throughout the year.1 Anyone can catch norovirus, as it spreads easily through close contact, contaminated food/water or contaminated surfaces. Symptoms tend to develop rapidly, and although most people recover quickly, some individuals may face serious symptoms which can result in dehydration, and on some occasions, even death. Even though some people may never show any signs of norovirus, they can still spread it to others easily. 

Therefore, as winter approaches, understanding the impact of norovirus is crucial to ensure the safety of your family, especially in individuals who are prone to having serious symptoms; this includes young children, the elderly, and people with weakened immune systems (immunocompromised). Additionally, it is important to be aware of the differences that norovirus presents in children compared to the elderly population, as well as the extent to which norovirus differs across age groups. 

History and virology of norovirus

Noroviruses are a genetically diverse class of viruses in the Caliciviridae family that cause severe gastroenteritis. In 1968, an outbreak in Norwalk, Ohio, USA, led to the discovery of the first norovirus known as the “Norwalk virus,” which was found after a stool sample showed the viral particle via electron microscopy. It was revealed that the Norwalk virus was the first virus to cause gastroenteritis.²

Although there have been other viruses found that resemble the symptoms of the Norovirus, noroviruses are currently categorised into genogroups from GI to GVII. Infectious diseases in humans are known to be caused by the specific genogroups GI, GII, and, to a lesser extent, GIV. The predominant cause of norovirus sickness around the world is viruses with the GII.4 genotype, which also give rise to new variants every 2 to 4 years.³ 

In other words, norovirus continuously evolves and adapts; this leads to the development of more severe symptoms, making it difficult for scientists to produce an antiviral treatment. Hence, at present, there are no specific treatments for norovirus. 

Transmission

The oral-faecal route is the most prevalent form of transmission for norovirus, which means that the virus particles in an infected person's faeces (stool) come into contact with their hands. This then comes in contact with another person's hands, and is then transmitted to the other person's mouth, infecting them. An infected person may also touch surfaces, food, or even water, which can transmit the virus to anyone who comes in contact with these items.⁴

General symptoms

Most people who contract a norovirus typically recover from their acute illness in 1 to 2 days, however, some may continue to feel unwell or experience symptoms for up to 6 days. Your body progressively eliminates the entire virus after the illness. In hindsight, the symptoms emerge quickly within a day or two after being infected. The general symptoms of norovirus include the following:⁴

• Diarrhoea 
• Vomiting 
• Nausea 
• Headache
• Body aches, particularly in the arms and legs
• Fever
• Chills
• Abdominal and/or stomach pain
• Fatigue/lethargy

Norovirus in children

Children, especially those who are younger than 5 years old, are at a greater risk of catching norovirus in comparison to other age groups in the community.⁵ Babies are born with a reliance on maternal antibodies; these are proteins that have been passed from the mother through breastfeeding, which helps the baby’s immune system to defend against bacteria during the first few months of life. As the child grows older, their immune system strengthens over time from exposure to pathogens and a series of vaccines. The immune system continuously develops throughout our life expectancy; however, by the age of two, it has established the key important functions. By ages 7 to 8, it has reached significant maturation, and continues to do so until it reaches maximum immunological competence in late adolescent years.⁶

Children younger than 5 are more likely to be exposed to norovirus at nursery and primary school. This means that although they are more likely to develop the general symptoms, they are at a greater risk of being dehydrated compared to adults. Considering their underdeveloped immune systems and an easy gag reflex, vomiting is a child’s predominant response to viral illnesses, which leads to a loss of fluid. Other symptoms may include:

• Watery diarrhoea
• Mild fever
• Body aches 
• Lack of energy 
• Crying more often and/or tantrums
• Irritability

It is, therefore, crucial to ensure that a sick child stays hydrated to avoid the risk of hospitalisation. Severe dehydration may present as:⁷

• A sunken area on top of their head, called a fontanelle, has formed 
• Dry mouth
• Sunken eyes, with few or no tears when they cry
• Having fewer wet nappies in babies
• Urinating less often
• Feeling sleepy or agitated

Norovirus in adults and teens

Compared to children, adults and teenagers have stronger immune systems. This means that the recovery rate will be much faster than a child, as they are equipped with antibodies and a stronger defence line against the virus. Whilst vomiting is more likely to be a child’s response to viral infections, adults and teenagers are more likely to experience diarrhoea due to the norovirus causing the intestinal lining to alter, which results in the cells releasing fluids that are eventually flushed out of the body. 

Individuals who are immunocompromised and older adults may be prone to malnutrition due to insufficient nutrients. Alongside this symptom, they are at a higher risk of exhibiting similar symptoms to children, and therefore, are at a higher risk of dehydration if there is insufficient fluid in the body. 

Key differences in impact

Below is a table with the key differences in the impact of norovirus between children, compared to adults and teens. 

Table 1. Differences in norovirus across age groups.

Prevention and management

As previously mentioned, there are no treatments available for norovirus. Producing antibiotics is also not possible, as norovirus is a viral infection, and antibiotics are only effective against infections caused by bacteria. Nevertheless, there are ways to manage the symptoms and prevent any further infections at home. 

Hygiene practices

Ensure that every member of your household often washes their hands with soap for at least 15 seconds, especially when entering and leaving your home, using the lavatory, and before eating or handling any food, in order to prevent any norovirus infections in your home during an outbreak. 

It is recommended to wash your hands with soap instead of using hand sanitisers as a substitute, as they do not work effectively against norovirus. 

If you are sick with norovirus, please ensure that:

• Contaminated surfaces are thoroughly cleaned right away with hot, soapy water
• A disinfectant is applied to sanitise the area
• Food is handled carefully; fruits and vegetables are washed thoroughly, and kitchen utensils are routinely cleaned and sanitised
• Clothing or linens that may be contaminated with vomit or stool are removed right away and washed with hot water, detergent, and bleach⁸

Hydration and rest

Allow yourself plenty of rest. Drink water and oral rehydration solutions to replace the fluids lost from diarrhoea and vomiting, in order to prevent dehydration. Although food may not be appetising when you are vomiting, try to have smaller, bland meals (i.e. pasta, bread or rice) frequently throughout the day instead of large meals. 

Staying at home

When you're unwell, it's crucial to stay at home to prevent spreading your illness to other people. Do not cook, handle food, or take care of other people. Allow the symptoms to go away for at least 48 hours. This is especially important if you work in an establishment like a restaurant, school, nursery, or long-term care facility where you could potentially expose others to the norovirus.

Medical attention 

Take over-the-counter medication, such as paracetamol, for any headache or body aches.

If you think your child has a norovirus and they experience any of the following symptoms, call 999 immediately or seek medical help:⁹

• Vomiting blood 
• Green/yellow-green vomit or vomit that appears like ground coffee 
• Experiencing pain and a stiff neck from staring at bright lights
• Sudden headache or stomach ache

Summary

Norovirus is a group of contagious viruses which cause gastroenteritis. Infections commonly occur in the winter season, and anyone can contract them. It can spread through consuming contaminated food or water, or by touching any contaminated surfaces. Although all individuals experience similar symptoms, children are more prone to vomiting due to a weaker immune system, which can lead to dehydration. Adults and teenagers who are not immunocompromised or are from the older population are quicker to recover with minimal difficulties. Although there is no known cure for norovirus, there are some at-home management strategies you can implement, such as rest, fluids, and over-the-counter painkillers. Overall, preventing the norovirus with practices like eating and personal hygiene is the best approach to manage it.