Norovirus

• Norovirus, spread by the faecal-oral route — from contaminated hands, surfaces, food or water, and by aerosolised particles from vomiting
• It takes very few viral particles to infect someone, which is why it moves through households, schools, cruise ships, hospitals and care homes so efficiently
• Winter peaks, though it circulates all year
• Contaminated shellfish, particularly oysters, and salad or fruit washed in contaminated water
• Surfaces — the virus survives on hard surfaces for days

Why you keep getting it

Immunity is short-lived and strain-specific. Having had norovirus this winter does not protect you next winter, or even necessarily from a different strain this winter. There is no vaccine.

Who is at greater risk of complications

Babies and young children, older adults, people who are immunosuppressed, and anyone with a condition where dehydration is dangerous — including people on diuretics, ACE inhibitors or SGLT2 inhibitors, and those with kidney disease or diabetes.

Clinically, and usually not at all

Sudden vomiting and diarrhoea in an otherwise well person, lasting a day or two, particularly during an outbreak or in winter, needs no test. The diagnosis does not change the management.

When a stool sample is worth doing

• Blood or mucus in the stool
• Diarrhoea lasting more than seven days
• Recent foreign travel — different organisms, and some need specific treatment
• Recent antibiotics or hospital admission — testing for C. difficile
• Anyone immunosuppressed, or systemically unwell
• Suspected outbreaks in schools, care homes or hospitals, where public health needs to know
• Food handlers and healthcare workers, where clearance may be required

Blood tests

Kidney function and electrolytes where dehydration is significant, particularly in older people or anyone on medication affected by it.

What else it might be

Bacterial food poisoning (campylobacter, salmonella — usually more fever and often blood), C. difficile after antibiotics, appendicitis (pain first, then vomiting), diabetic ketoacidosis, a urine infection in an older person, and inflammatory bowel disease where diarrhoea persists.

The order matters: in gastroenteritis, vomiting and diarrhoea usually come before or with the pain. Pain first, then vomiting, is a surgical pattern until proven otherwise.

Soap and water, not gel

Alcohol hand gel is not effective against norovirus. The virus lacks the outer envelope that alcohol disrupts.

Wash with soap and warm water for at least 20 seconds, particularly after using the toilet, after caring for someone unwell, and before handling food. This is the single most important measure and it is routinely undermined by reliance on gel.

Cleaning up

• Use a bleach-based cleaner on contaminated surfaces — ordinary detergents do not reliably inactivate norovirus
• Clean up vomit and diarrhoea promptly, wearing gloves, and disinfect the area and everything around it
• Wash contaminated clothing and bedding separately on a hot wash
• Do not vacuum areas contaminated with vomit, which aerosolises the virus
• Flush with the toilet lid down

Rehydration — the actual treatment

• Small amounts, frequently. A few sips every ten minutes stays down far better than a glass at once
• Oral rehydration salts from a pharmacy are genuinely better than water alone for significant losses, because they replace salts as well as fluid
• Avoid fizzy drinks and undiluted fruit juice, which can worsen diarrhoea
• Keep breastfeeding or formula feeding a baby, and offer extra fluids between feeds
• Eat when you feel able. The old advice to starve yourself has gone — ordinary food as tolerated is better

The 48-hour rule

Stay off work, school or nursery until 48 hours after symptoms have completely stopped — not 48 hours after they started, and not as soon as you feel better. You remain infectious during that window.

This matters most for food handlers, healthcare and care home staff, and anyone visiting a hospital or care home. Norovirus outbreaks in those settings cause genuine harm to people who are already unwell.

Does hand gel work against norovirus?

No — and this is the most useful thing on the page. Norovirus has no outer envelope for alcohol to break down.

Soap and water for 20 seconds is what works. Relying on gel is a significant reason outbreaks keep spreading.

When can I go back to work?

48 hours after symptoms have completely stopped — not from when they started, and not as soon as you feel better.

Stricter rules apply if you handle food or work in health or social care.

Do I need antibiotics?

No. It is viral, and antibiotics do nothing except cause diarrhoea of their own.

Should I stop eating?

No — that advice has been superseded. Eat what you can manage as your appetite returns.

Fluids are the priority, in small frequent amounts rather than large drinks.

Is Dioralyte better than water?

For significant fluid losses, yes. It replaces salts as well as water, which plain water does not.

Worth having in the cupboard, particularly with young children or older relatives at home.

Can I take Imodium?

Usually unnecessary, and not always safe. Avoid it entirely in children, and in anyone with a fever or blood in the stool.

In an otherwise well adult with watery diarrhoea it is reasonable occasionally, but it treats the symptom rather than the illness.

Should I stop my usual tablets?

Temporarily, some of them — and this genuinely matters. ACE inhibitors, ARBs, diuretics, anti-inflammatories, metformin and SGLT2 inhibitors are paused while you are vomiting and dehydrated.

Restart after a day or two of normal eating and drinking. This prevents avoidable kidney injury.

Why do I keep catching it?

Immunity is short-lived and strain-specific. Having had it does not protect you for long, and there is no vaccine.

How long am I infectious?

From before symptoms start until at least 48 hours after they stop — and the virus can be shed in stool for a week or more afterwards.

Which is why handwashing continues to matter after you feel well.