Norovirus Infection
Also known as Winter vomiting bug, Viral gastroenteritis
This article is general health information for the selected condition. It is not a diagnosis and does not replace clinical judgement. If you have questions or need treatment advice, please consult a qualified healthcare professional.
What is norovirus infection?
Norovirus is the most common cause of infectious gastroenteritis and outbreaks in hospitals, care homes, schools and cruise ships. It causes abrupt vomiting and diarrhoea, usually resolving within one to three days. It spreads very easily, and alcohol hand gel does not kill it, so soap and water handwashing is essential.
Causes
- Norovirus transmitted by the faecal oral route
- Contaminated food, particularly shellfish and salads
- Contaminated surfaces and objects
- Aerosolised particles from vomiting
- Very low infectious dose
Symptoms
- Sudden onset vomiting, often projectile
- Watery diarrhoea
- Stomach cramps
- Nausea
- Low grade fever and muscle aches
- Symptoms typically lasting 12 to 72 hours
Risk factors
- Closed or crowded settings
- Healthcare and care home environments
- Food handling occupations
- Winter months
- Age extremes for severe dehydration
Diagnosis
- Clinical diagnosis from the abrupt symptom pattern
- PCR stool testing during outbreak investigation
- Assessment of hydration status
- Electrolyte testing where dehydration is significant
Treatment
- Oral rehydration with small frequent sips
- Rest and gradual return to eating
- Intravenous fluids if dehydration becomes severe
- Thorough handwashing with soap and water
- Cleaning surfaces with bleach based products
- Staying away from work or school for 48 hours after symptoms stop
Self care
- Sip oral rehydration solution frequently
- Rest and return to plain food gradually
- Wash hands with soap and water rather than relying on gel
- Clean surfaces with a bleach based product
- Do not prepare food for others while ill
- Stay away from work, school and hospitals for 48 hours after symptoms stop
- Wash soiled laundry separately on a hot cycle
When to see a doctor
Book an appointment if:
- Symptoms lasting more than three days
- Unable to keep fluids down
- Blood in the stool
- Existing kidney disease, diabetes or reduced immunity
- An infant or older adult with persistent vomiting
- Recent hospital admission with new diarrhoea
Some symptoms need emergency care rather than an appointment. See the warning signs listed above.
Prevention
- Wash hands with soap and water, especially after using the toilet
- Isolate cases promptly in shared settings
- Clean contaminated surfaces with bleach
- Avoid preparing food for others until 48 hours symptom free
- Wash fruit and vegetables and cook shellfish thoroughly
Outlook
Norovirus is unpleasant but short lived, typically resolving within one to three days with supportive care. Complications are almost entirely related to dehydration, which is why the very young, older adults and those with chronic disease need closer attention. Immunity is short lived so reinfection is common.
Common questions
Why does hand sanitiser not work well?
Norovirus has no lipid envelope, so alcohol gels are relatively ineffective against it. Washing with soap and running water physically removes the virus and is the recommended method during outbreaks.
How long am I infectious?
Virus is shed from before symptoms start until at least two days after they stop, and sometimes for weeks. The standard advice is to stay away from work, school and hospitals for 48 hours after the last episode.
Can you catch it more than once?
Yes. Immunity is short lived and there are many strains, so repeat infections are common across a lifetime and even within the same season.
References
Important: Dard AI is not a medical device and does not diagnose, treat, or replace clinician judgement. This article is general information only. Always consult a qualified healthcare professional about diagnosis and treatment, and seek emergency care for severe or rapidly worsening symptoms.