Norovirus
A very contagious viral gastroenteritis that causes sudden vomiting and diarrhea and spreads readily in homes, schools, restaurants, hospitals, and cruise ships.
What causes Norovirus?
Norovirus infection is caused by a group of caliciviruses. It spreads through tiny amounts of infected stool or vomit on hands, food, water, surfaces, and aerosolized droplets produced during vomiting.
Symptoms and what to notice
Sudden nausea, vomiting, watery diarrhea, stomach cramps, and sometimes low fever, headache, or body aches. Dehydration can cause reduced urination, dry mouth, dizziness, or unusual sleepiness.
How long can it last?
Symptoms usually begin 12 to 48 hours after exposure and most people improve within 1 to 3 days, although viral shedding can continue after recovery.
How serious is Norovirus?
Dehydration can require medical treatment, especially in infants, older adults, and people with chronic illness or weakened immunity. Outbreaks can disrupt healthcare and long-term-care facilities.
Treatment and management
There is no specific approved antiviral. Oral rehydration is central; severe dehydration may require intravenous fluids. Antibiotics do not treat norovirus, and anti-diarrheal or anti-vomiting medicines should be used only when appropriate for the patient.
Vaccine: who and when?
No licensed norovirus vaccine is available in the United States as of September 2026. Vaccine candidates remain in clinical development, so prevention depends on handwashing with soap and water, safe food handling, isolation, and effective environmental disinfection.
Cost note: Patient cost varies by product, provider, insurance, location, and eligibility. Many recommended vaccines are covered in network without cost sharing, and qualifying children may use the Vaccines for Children program.
Trusted source
Patient cost varies by insurance, provider, location, and eligibility. Coverage and public-health access differ, so listed prices are examples rather than guaranteed patient prices. This page is for general education and does not replace individualized medical advice, diagnosis, vaccination assessment, or treatment.
Norovirus: Symptoms, Causes, Treatment, Prevention, and Vaccine Information
Norovirus is the leading cause of acute vomiting and diarrhea outbreaks across all ages. Only a small amount of virus is needed to infect someone, and particles can persist on surfaces. Short incubation, explosive vomiting, and continued shedding after recovery make control difficult. Most illness is brief, but fluid loss can become dangerous.
Important: This page is for general education. It does not replace diagnosis, treatment, vaccination advice, or emergency care from a qualified healthcare professional.
Quick Facts
| Topic | Current information |
|---|---|
| Cause | Norovirus infection is caused by a group of caliciviruses. It spreads through tiny amounts of infected stool or vomit on hands, food, water, surfaces, and aerosolized droplets produced during vomiting. |
| Main symptoms | Sudden nausea, vomiting, watery diarrhea, stomach cramps, and sometimes low fever, headache, or body aches. Dehydration can cause reduced urination, dry mouth, dizziness, or unusual sleepiness. |
| Typical course | Symptoms usually begin 12 to 48 hours after exposure and most people improve within 1 to 3 days, although viral shedding can continue after recovery. |
| Treatment | There is no specific approved antiviral. Oral rehydration is central; severe dehydration may require intravenous fluids. Antibiotics do not treat norovirus, and anti-diarrheal or anti-vomiting medicines should be used only when appropriate for the patient. |
| Vaccine status | No licensed norovirus vaccine is available in the United States as of September 2026. Vaccine candidates remain in clinical development, so prevention depends on handwashing with soap and water, safe food handling, isolation, and effective environmental disinfection. |
History and Public-Health Importance
Norovirus was first recognized through an outbreak in Norwalk, Ohio, in 1968. Molecular testing later revealed many genotypes and frequent strain changes. Surveillance links outbreaks to healthcare facilities, restaurants, schools, camps, ships, and contaminated foods. Control relies on rapid recognition, exclusion of ill workers, cleaning, and hand hygiene because durable immunity and a licensed vaccine are lacking.
What Causes Norovirus?
Norovirus infection is caused by a group of caliciviruses. It spreads through tiny amounts of infected stool or vomit on hands, food, water, surfaces, and aerosolized droplets produced during vomiting.
People become infected by eating contaminated food, drinking contaminated water, touching contaminated surfaces and then the mouth, or caring for someone who is ill. Vomiting can disperse droplets onto nearby surfaces. Infected food handlers are a common source of outbreaks. Alcohol hand sanitizer is not a substitute for thorough soap-and-water washing against norovirus.
Symptoms and Typical Course
Sudden nausea, vomiting, watery diarrhea, stomach cramps, and sometimes low fever, headache, or body aches. Dehydration can cause reduced urination, dry mouth, dizziness, or unusual sleepiness.
Vomiting may be prominent in children, while adults often have more diarrhea. Cramps, nausea, low fever, headache, and aches can accompany illness. Most people recover in one to three days, but fatigue can persist. Immunocompromised patients can have prolonged diarrhea and shedding.
Complications and Who Is at Higher Risk
Dehydration can require medical treatment, especially in infants, older adults, and people with chronic illness or weakened immunity. Outbreaks can disrupt healthcare and long-term-care facilities.
The main danger is dehydration and electrolyte imbalance. Infants may produce fewer wet diapers; older adults may become dizzy, confused, or weak. Severe fluid loss can cause kidney injury or shock. Chronic illness, pregnancy, frailty, and inability to keep fluids down increase concern.
How It Is Diagnosed
Most individual cases are diagnosed clinically. RT-qPCR testing of stool is used in outbreaks, severe cases, or public-health investigations. Testing can identify a norovirus genogroup but does not change routine supportive treatment. Other causes, including bacteria, toxins, and medications, may need evaluation when illness is severe or atypical.
Treatment and Recovery
There is no specific approved antiviral. Oral rehydration is central; severe dehydration may require intravenous fluids. Antibiotics do not treat norovirus, and anti-diarrheal or anti-vomiting medicines should be used only when appropriate for the patient.
Use small, frequent sips of oral rehydration solution, which replaces water and electrolytes more effectively than many sugary drinks. Breastfeeding should continue when tolerated. Intravenous fluids are used for severe dehydration. Antibiotics are ineffective. Clinicians decide whether symptom medicines are safe based on age, pregnancy, fever, bloody stool, and other conditions.
Vaccine Information
No licensed norovirus vaccine is available in the United States as of September 2026. Vaccine candidates remain in clinical development, so prevention depends on handwashing with soap and water, safe food handling, isolation, and effective environmental disinfection.
No FDA-approved norovirus vaccine exists. Multiple candidates, including virus-like-particle and other platforms, have entered clinical trials, but none is available for routine or outbreak use. Prior infection does not reliably protect against different strains or future illness.
Prevention
Wash hands with soap and water for at least 20 seconds, especially after toilet use or diapering and before food preparation. Do not prepare food or care for others while sick and for at least 48 hours after symptoms stop. Wash contaminated laundry hot, clean vomit and stool promptly, and use an EPA-registered product effective against norovirus or an appropriate chlorine solution.
When to Seek Medical Care
Seek care for inability to keep fluids down, very little urination, bloody stool, severe abdominal pain, confusion, fainting, or symptoms in a vulnerable infant, frail older adult, pregnant person, or immunocompromised patient.
Frequently Asked Questions
Is norovirus the same as stomach flu?
It is often called stomach flu, but it is unrelated to influenza, which primarily affects the respiratory tract.
Does hand sanitizer kill norovirus?
It may reduce some germs but is less reliable against norovirus; soap-and-water handwashing is preferred.
Can people spread it after feeling better?
Yes. Shedding continues after recovery, so careful hygiene and food-worker exclusion remain important.
Is there a vaccine?
No licensed vaccine is available in the United States as of September 2026.
Key Takeaway
Norovirus spreads with extraordinary efficiency. Rehydration prevents most complications, while soap-and-water handwashing, exclusion of ill food handlers, and correct disinfection stop outbreaks.
Medical, treatment, and vaccine information was reviewed against official U.S. public-health guidance available through September 2026.