What is norovirus and how can you prevent infection?
As winter carries on, cases of norovirus are increasing. Norovirus, also known as the winter vomiting bug, threatens every UK household, with an estimated 3.7 million people in the UK contracting the virus every year, and 200,000 people dying from it worldwide. New data published by the NHS recently highlight a ‘surge’ in norovirus cases in hospitals, about 80 per cent higher than the same period a year ago. In fact, NHS hospitals are seeing the highest level of the virus recorded since January 2020.
The bug is brutal, highly contagious, and has huge consequences – often closing hospital wards and taking children and parents out of school and work.
Thankfully, in October 2024, it was announced that the world’s first vaccine is being developed in the UK to treat norovirus. Sadly, however, it won’t be available until 2026 so we won’t be able to get our (hopefully sanitised) hands on it yet.
“Norovirus can mutate easily, similar to other viruses like influenza and Covid,” says Lucy Thorne, a lecturer in molecular virology at Imperial College London. “A vaccine can provide beneficial short-term protection, and it might be the case that you may need a booster every year, especially for high-risk groups.”
What exactly is norovirus?
Norovirus is a virus that causes diarrhoea, sickness, and stomach pain, and the most common cause of acute gastroenteritis, an inflammation of the stomach and intestines. It is most contagious from the start of symptoms until 48 hours after all symptoms have stopped.
The infected person may feel very sick and vomit often, sometimes without warning, many times a day. Strangely, sometimes the infected person can have no symptoms at all, but can still pass the virus to others.
What are the symptoms of norovirus?
They are not pleasant and are two-fold. Norovirus typically causes diarrhoea and projectile vomiting – often at the same time, which has earned it the nickname of the “Two Bucket Disease”, says Thorne. This is accompanied by the following:
Stomach cramps
Muscle aches
Fever
In small children it can also cause seizures linked to having a high fever. “It’s not known exactly how the virus causes the seizures, but it infects and damages the cells that line your intestines.”
The graphic below shows how norovirus can affect your body.
How does norovirus spread?
Norovirus can be contracted and spread after having direct contact with someone who’s been infected by the bug, or touching a surface that has been contaminated by an infected person, and then putting your hand near your mouth.
“It is spread through projectile vomit onto surfaces,” says Thorne. “Small particles of vomit, that become aerosolised [turn into a fine mist], can carry the virus up to 9ft. This creates a huge area that would need decontaminating if vomit isn’t contained.
Thorne adds: “It’s also spread by the faecal-oral route, which means from poo to mouth, most likely by an infected person’s hands contaminating surfaces so that someone else picks it up and touches their mouth.”
How contagious is norovirus?
Extremely. Studies on volunteers have told us that you need as little as 20 viral particles to become infected. To give that some context: one teaspoon of infected faeces can contain up to five billion virus particles, which in theory could produce enough of the virus to infect everyone on the planet.
Thorne says: “Of course this doesn’t happen, but it shows you how important it is to try and contain it and how crucial hygiene is to clear and inactivate the virus. It’s very stable, can persist on surfaces and stay infectious for several weeks, which gives it more chance of being picked up by someone or contaminating food.”
What food is norovirus found in?
The foods that are most often linked to norovirus include:
Leafy greens
Fresh fruits
Shellfish
Many norovirus outbreaks linked to food happen in restaurants or at catered events when infected workers touch ready-to-eat foods. Outbreaks stem from food that’s contaminated on a farm, such as oysters harvested from contaminated water or fruit, and vegetables that are sprayed with contaminated water in a field, the Centre for Disease Control (CDC) reports.
“Cooking can inactivate the virus, so it’s often only a problem when eaten raw. It has also been linked in some cases to salads and some fruits that have been washed in contaminated water or touched by infected food handlers, but this is much less common,” says Thorne.
What to do if you have norovirus
If you have norovirus, stay at home until symptoms go away.
Unfortunately you have to let the illness run its course. Just be aware that you can still spread norovirus to others, even after symptoms disappear.
“People can still remain infectious even after a couple of weeks – so even if you feel better you still need to be careful. It’s your responsibility to limit its spread and avoid contact with people,” says Dr Ahmed Albusoda, a gastroenterologist at Princess Grace Hospital. “This way, it has less impact on the community and people’s health until hopefully the vaccine comes along.”
The NHS recommends that you:
Avoid cooking meals for the rest of the household, as you might make them sick.
Avoid sharing everyday items like towels, bedding, and dishes.
Eat bland and non-spicy foods, so as not to irritate the stomach.
Rest, stay hydrated, and take paracetamol for the aches and pains.
In most cases, you won’t need to go to doctor. But, if symptoms persist for longer than three days, it’s important to see one.
How long does norovirus last?
For most healthy adults, symptoms will last one to three days before the infection clears naturally.
“It’s most dangerous for the very young and elderly, who are at risk of dehydration and complications, and people with compromised immune systems. They can develop chronic infections which can last for years with serious complications,” says Thorne.
What food should you avoid if you have norovirus?
Dr Albusoda has the following advice:
“Avoid foods which are harder to digest like fatty and fried food, heavy proteins like steaks and spicy food. They need a lot of work to disintegrate,” he says “When the bowel is inflamed, it becomes very sensitive, so you want food which is simple to digest.
“Also avoid milk and dairy products as the virus can kill the bacteria which helps you digest them – this may make you more sensitive and bloated.
“Focus on food like plain white rice, banana, bread or toast which is easily digested and helps improve the consistency of the stool.
“Stay hydrated and sip on water every hour to replenish what your body is losing. It’s also important to replace the electrolytes lost through dehydration which can be done by sipping sports drinks or rehydration solutions.”
How can you protect yourself?
Thorne advises: “The best way to protect yourself is through really good hand hygiene, washing your hands with hot soapy water before you eat, or if you have been around someone who has symptoms that match norovirus.”
Take measures to disinfect your house too. “Cleaning your house thoroughly after someone has been ill – and in a wider area than just the spaces that have been immediately in contact – imagine 9ft around wherever the infected person has been,” adds Thorne. Make sure any items that could have been contaminated with the virus is washed separately on a hot wash. “Not keeping your toothbrushes on a shelf near the toilet is also a good idea if someone is ill!”
Many disinfectants won’t kill it and alcohol doesn’t kill norovirus – use a bleach-based cleaner.
Experts also recommend avoiding taking ibuprofen on an empty stomach, as it can upset the stomach lining. The NHS advises against eating raw and unwashed foods.
Is there a cure for norovirus?
“There is no cure for norovirus right now, but doctors will help treat the symptoms. For infections in immunocompromised individuals, norovirus can be serious and long term. In this case, you should seek professional help to support hydration, nutrition and discuss potential treatment options,” says Thorne.
A vaccine for norovirus is currently in the works, but in the meantime, if you get norovirus make sure you stay at home to prevent spreading the virus to others.
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