What Is Norovirus?

Noroviruses are a group of very common and highly contagious viruses that cause diarrhoea and vomiting, predominantly in the wintertime. Norovirus is more common in the winter because the virus takes longer to break down in the colder weather and lower sunlight levels, so remains for longer.¹ They infect people by causing gastroenteritis (inflammation of the stomach lining and intestines). The viruses easily spread between people, so if you develop norovirus symptoms you should try not to come into contact with others. The symptoms tend to come on rapidly and last for up to two days. 

What is the history of norovirus? 

Noroviruses were first found in the population in 1968 when half of the pupils at a school in Norwalk, Ohio in the US became ill, showing symptoms of gastroenteritis.² When stool samples were taken from the infected individuals and administered orally to prisoners in Maryland, they also showed symptoms of gastroenteritis, proving the mode of spread. 

It wasn’t until 1972 that scientists could view the virus using a technique called electron microscopy. 

What are the symptoms of norovirus?

The key symptoms of norovirus are as follows: 

• Diarrhoea 
• Vomiting 
• Nausea 
• Stomach pain
• Abdominal cramps
• Fever and chills
• Headache
• Aches in the body 
• Lethargy

Due to the loss of water and electrolytes from sickness and diarrhoea, you can easily become dehydrated if you have norovirus. So, it is important to note the following symptoms of dehydration: 

• Urinating less often
• Throat and mouth feeling dry 
• Dizziness when standing 

Symptoms usually present up to 48 hours after exposure to the virus. If you think you may be infected by norovirus, you can treat the infection at home. But, if diarrhoea persists and does not go away after multiple days, or if you experience severe vomiting, blood in your stools, or stomach pain, it is important to speak to your healthcare provider to get the right treatment. If you are unable to replace the fluids you lose, you may be given them at the hospital through a tube inserted into your vein. 

While some people will not experience any symptoms of norovirus, they can still easily pass it on to others. 

Who can get norovirus? 

Norovirus is very common and is responsible for one out of every five cases of gastroenteritis. It is believed that 685 million people are infected with norovirus each year, with 200 million being young children under five years old. Norovirus causes 50,000 child deaths each year, predominantly in developing countries where economic deficiencies, inadequate infrastructure, poor hygiene, and overcrowding are more prevalent. That said, norovirus burdens the healthcare system in both high and lower-income countries, costing as much as $60 billion in healthcare expenses and decreasing productivity each year. 

Anyone can be infected by norovirus, and they can contract the infection multiple times. Those most at risk of severe and longer norovirus infections include the elderly, young children and infants, and people with underlying medical conditions and weakened immune systems. Public spaces that are often crowded such as childcare facilities, schools, and leisure centres are higher risk places for the spread of norovirus, due to the high number of opportunities for person-to-person interaction. 

What are the causes of norovirus?

Noroviruses are commonly spread in food outlets, schools or nurseries, hospitals, and other busy public spaces. The infographic below shows some of the common causes and risk factors associated with norovirus:³

Image source: Parr-Reid S. Canva. 

The most common method of transmission for norovirus is known as the oral-faecal route, meaning virus particles present in faeces (poo) of an infected person come into contact with their hands and subsequently another person’s hands, and are then passed to the other person’s mouth, infecting them. Norovirus only needs to be present in a low dose to infect a person - as little as 18 virus particles.⁴ It is also able to withstand both high and low temperatures, making it easy to survive inside and outside of the body. Since you do not develop immunity to the infection following illness, noroviruses can continue to infect you over time. 

How is norovirus diagnosed?

Usually, a diagnosis of norovirus is made only from the symptoms,⁴ but tests can be used to confirm the diagnosis. For example, a stool sample can be taken to identify the presence of norovirus particles which shed and are excreted in stools. While the shed virus particles are too small to see with the naked eye, they can be seen through a microscope. 

How is norovirus treated? 

There isn’t a specific treatment for norovirus, but instead several ways to manage the infection until you get better. Listed below are some of the ways you can manage norovirus at home: 

• Drink lots of water and fluids to replace water lost through vomiting and diarrhoea 
• Get as much rest as you can while you recover
• Take over-the-counter pain relief, such as paracetamol, for any aches or pain
• When you can, try to eat dry and plain foods like bread, pasta and rice 
• Take over-the-counter rehydration solutions to help restore your water and electrolytes 

Preventing the spread of norovirus 

There are several important ways that you can prevent the spread of norovirus both at home and in public spaces. The infographic below shows some of the key ways you can prevent the spread of norovirus:⁵

Image source: Parr-Reid S. Canva. 

Summary 

Noroviruses are a group of viruses that infect the stomach and intestines by causing inflammation. This inflammation can cause vomiting and diarrhoea, as well as fever, aches, and lethargy. Norovirus infections are very common, especially during the winter. It passes from person to person through touching contaminated surfaces or ingesting contaminated food or water. The spread of norovirus mostly happens when viruses in the stool of an infected person come into contact with their hands and then another person through touch. Norovirus is not normally investigated by a healthcare provider and can be diagnosed from symptoms alone. Whilst there is no specific treatment for norovirus, there are lots of ways to manage it at home including over-the-counter pain relief, rest, and rehydration. Overall, the best way to manage norovirus is through prevention, such as good personal and food hygiene.