What is norovirus, how do you prevent it, and are cases rising?

The number of people in hospital with winter viruses such as norovirus are "creeping up", NHS England has warned, with some hospitals banning visitors to prevent further infections.

Last week the number of people in hospital with norovirus was up 15% on the previous week, to an average of 406 people per day, the health service said. This marked a 28% increase on the same week last year. It added that an average of 92 beds were closed each day last week in a bid to stop the virus spreading among other patients.

Norovirus is the most common infectious cause of diarrhoea and vomiting, and cases normally rise during the winter months. Nonetheless, concerns have been raised that a surge this year will put significant pressure on hospital wards.

However, a rise in norovirus hospital patients doesn't necessarily mean there's a widespread national outbreak, and separate data from the UK Health Security Agency (UKHSA) paints a slightly different picture. Here, Yahoo News explains the common symptoms of norovirus, what to do if you have it, and why there is a discrepancy in UK case numbers.

Recommended reading

• Winter vomiting bug shuts three wards at North East hospital in 'worst outbreak' (The Northern Echo)

• Students struck down with norovirus outbreak after $1 burrito event (The Independent)

• Norovirus surge forces hospitals to ban visitors (The Telegraph)

What is norovirus and what are its symptoms?

Norovirus, also known as the "winter vomiting bug", is a stomach bug that causes vomiting and diarrhoea, according to the NHS. It is the most common cause of gastroenteritis (inflammation of the stomach and intestines), and also causes stomach pain.

Other symptoms can include a high temperature, a headache, and aching arms and legs. Symptoms usually appear within one to two days of being infected, and typically last for two to three days.

How does norovirus spread?

Unfortunately, norovirus can spread very easily, the NHS warns. People can pick it up from close contact with someone who's infected, who may breathe out small particles of the virus that the other person inhales.

Touching a surface with the virus on it and then touching your mouth is another way to catch the bug, which can survive outside a human body for several days.

Eating food that has been prepared or handled by someone with norovirus is another common cause of infections – especially if they haven't washed their hands.

How can I prevent norovirus?

The best way to prevent the spread of norovirus is to maintain basic hygiene around the house. This includes using bleach-based household cleaner to disinfect any surfaces or objects that could be contaminated, the NHS advises.

If you think you've had the virus, you should wash any items of clothing or bedding that could have been contaminated separately, on a hot wash (60C), in order to kill the virus. You should also avoid sharing towels and flannels with anyone you live with.

After flushing faeces or vomit in the toilet, be sure to clean the surrounding area with a bleach-based household cleaner, the NHS recommends. It also advises to avoid eating raw, unwashed food, and to only eat oysters from reliable sources, as they can carry the virus.

Those with the virus should stay off work or school until at least 48 hours after the norovirus symptoms have stopped and should wash their hands thoroughly with soap and water particularly after using the toilet and before handling food. The NHS warns that alcohol-based hand gels don’t kill norovirus.

How serious is norovirus, and what should I do if I have it?

Generally, doctors advise people to stay at home if they have sudden diarrhoea or vomiting and to let the virus run its course. There's no treatment for norovirus, and people with it don't usually need medical attention unless there's a risk of a more serious problem.

Be sure to drink plenty of fluids to avoid becoming dehydrated, as your body will lose more water than usual from the vomiting and diarrhoea. The NHS doesn't recommend giving fizzy drinks of fruit juice to children with the bug as it can make their diarrhoea worse, but says adults can try fruit juice and soup.

Babies should continue to feed as usual, either with breast milk or other milk feeds. People with norovirus should also take paracetamol for any fever or aches and pains, and get plenty of rest.

If an infected person is showing signs of dehydration they should try special rehydration drinks, which are available from many pharmacies. Both the elderly and very young are at higher risk of dehydration and may need hospital treatment because of it.

How much are cases really rising?

While the NHS has attributed a 28% year-on-year rise specifically to norovirus, the outlook may not be quite as simple as it seems. Data from the UKHSA shows that as of 26 November, norovirus lab reports were lower than the five year average.

While it does say that cases are up compared to previous weeks, this is the norm for the winter months. The UKHSA says that between November 13 and 26, lab reports of the virus were actually 16% lower than the five-season average for the same two-week period.

With this in mind, there could be a few reasons why hospitals are reporting an uptick in norovirus patients. The UKHSA points out that "norovirus activity in England has been more variable" since 2019/20, which is likely related to the aftermath of the pandemic.

It reports more "unusual activity" in the 2021/2022 season, "such as a greater proportion of outbreaks reported in educational settings than before the pandemic".

While vomiting and diarrhoea are common symptoms of norovirus, they can be caused by a number of other illnesses. Norovirus can be tested via stool samples, but it's often diagnosed based on symptoms.

The UKHSA adds that not all suspected cases are tested for norovirus, and that "often only a proportion of individuals will be tested in any suspected outbreak". Whatever the case, people should make the effort to prevent the spread of norovirus during the winter months, but these factors could help explain why different agencies are providing contrasting figures.