Norovirus, also known as the stomach flu, is a highly contagious virus that causes vomiting, diarrhea, and stomach pain. It is the leading cause of foodborne illness in the United States, responsible for up to 21 million cases each year. Norovirus infection is sometimes referred to as “stomach flu” or “food poisoning,” but it is not related to the flu or influenza viruses. Here are some key things to know about norovirus and how to identify if you may have contracted it.
What are the symptoms of norovirus?
The most common symptoms of norovirus include:
- Nausea
- Vomiting
- Diarrhea
- Stomach pain or cramps
- Low-grade fever
- Chills
- Headache
- Body aches
- Fatigue
Symptoms typically begin 12-48 hours after exposure to the virus. The illness is usually brief, with symptoms lasting 1-3 days. Some people may continue to feel fatigued for a few more days after other symptoms subside.
How does norovirus spread?
Norovirus spreads easily from person-to-person through the fecal-oral route. This means that microscopic particles from the vomit or stool of an infected person enter another person’s mouth.
Ways norovirus can spread include:
- Having direct contact with an infected person
- Consuming contaminated food or water
- Touching contaminated surfaces then putting fingers in your mouth
- Exposure to an infected person’s vomit or stool
Norovirus is extremely contagious. Only a small number of virus particles are needed to make someone ill. The virus can spread rapidly in crowded places like schools, childcare facilities, hospitals, nursing homes, cruise ships, and dormitories.
Who is most at risk for norovirus?
Anyone can get norovirus, but some groups are at higher risk including:
- Young children
- The elderly
- People with weakened immune systems
Young children under age 5 are especially vulnerable because they may not wash their hands properly and come into close contact with infected people. The virus also spreads rapidly in childcare settings.
Older adults living in nursing homes or assisted living facilities are also very susceptible due to shared facilities, close living quarters, and weakened immune systems. Outbreaks are common in long-term care settings.
Those with compromised or weakened immune systems, such as transplant recipients, cancer patients, or people with HIV/AIDS, are more likely to experience severe, prolonged illness from norovirus.
How is norovirus diagnosed?
Norovirus cannot be diagnosed through routine blood tests. Instead, doctors typically make a diagnosis based on symptoms and asking about exposure history. Diagnostic tests can be done on stool samples, but they are not routinely available.
If you have symptoms of vomiting, diarrhea, and stomach pain, your doctor will ask questions such as:
- When did the illness start?
- Have you been around anyone else who got sick?
- Did you recently eat at a restaurant, attend a function, or travel anywhere?
- Have you taken any medications or changed your diet recently?
Based on the symptoms and timing of the illness, norovirus is often suspected. Your doctor may order stool tests to rule out other potential causes like food poisoning from bacteria.
How is norovirus treated?
There is no specific medication used to treat norovirus. Antibiotics are also ineffective because it is a viral infection. Treatment focuses on managing symptoms and preventing dehydration by drinking plenty of fluids.
Recommendations for symptom relief and recovery include:
- Drinking water, juice, broth, or oral rehydration beverages
- Getting plenty of rest
- Eating bland, easy-to-digest foods like crackers, bread, rice, or noodles
- Avoiding dairy products, caffeine, alcohol, and spicy, fatty, or acidic foods until symptoms resolve
- Taking over-the-counter medications like Imodium or Pepto-Bismol for diarrhea
Infants, the elderly, and those with weakened immune systems may need medical attention and intravenous (IV) fluids to treat or prevent dehydration. Seek medical advice if symptoms don’t improve after a few days.
How can you prevent norovirus?
Practicing good hygiene and proper food handling are the best ways to prevent norovirus infection. Recommended prevention tips include:
- Washing hands thoroughly with soap and warm water, especially after using the bathroom and before eating or preparing food
- Avoiding close contact with anyone showing symptoms of norovirus
- Disinfecting contaminated surfaces with a bleach-based household cleaner
- Washing fruits and vegetables and cooking seafood thoroughly before eating
- Avoiding food or water from sources that may be contaminated
- Not preparing food while ill with vomiting or diarrhea
There are currently no vaccines to protect against norovirus. Good hand hygiene is the number one way to prevent transmission.
When are you contagious with norovirus?
People with norovirus are most contagious when they are exhibiting symptoms, but you can also spread the virus before symptoms start and for up to 2 weeks after you recover. Young children may spread the virus for several weeks after they feel better.
You are contagious:
- 1-2 days before symptoms start
- During the time you have symptoms
- For up to 2 weeks after symptoms resolve, although you are much less contagious after the first few days of illness
Proper handwashing is critical during this time to avoid spreading the virus to others.
How long does norovirus last?
The typical duration of a norovirus illness is 1-3 days. Most healthy people fully recover within a few days.
Symptoms usually start suddenly and last about:
- 12-48 hours – Vomiting and diarrhea are most severe
- 1-3 days – Other symptoms like nausea, abdominal pain, fever, chills, and body aches
- Less than 1 week – Fatigue and general weakness
In some cases, people may continue to feel tired and rundown for weeks after acute symptoms have passed. The elderly or those with compromised immune systems may also experience a prolonged recovery.
Even after symptoms have resolved, you can still shed virus particles in your stool for up to 2 weeks. Practicing good hand hygiene is important during the recovery phase.
Can norovirus be fatal?
Norovirus infection is usually mild and runs its course in a few days. Severe illness and death from norovirus is very rare, but can occur in vulnerable populations.
Those most at risk for severe disease include:
- Infants and young children
- Elderly adults over age 65
- Immunocompromised individuals
- Malnourished people
In these groups, severe vomiting and diarrhea can lead to dangerous electrolyte imbalances and dehydration. If not treated properly, it can be fatal. However, this represents only a very small percentage of norovirus cases.
Globally, there are approximately 200,000 deaths from norovirus each year, most occurring in developing countries. Proper medical care can greatly reduce the risks of fatal complications.
Key statistics on norovirus mortality
| Age Group | Risk of Death |
|---|---|
| Under age 5 | 25% of all norovirus deaths worldwide |
| Over age 65 | 75% of norovirus deaths in industrialized countries |
Can you get norovirus more than once?
It is possible to get norovirus repeatedly, even within the same season. This is because there are multiple different strains of norovirus circulating, and infection with one strain does not provide long-term immunity against others.
The main norovirus strains include:
- Genogroup I (GI)
- Genogroup II (GII)
Genogroup II viruses cause the majority of norovirus outbreaks worldwide. Examples of common GII strains include GII.4 Sydney, GII.2, GII.6, and GII.17.
Key points about norovirus immunity and reinfection:
- You can get norovirus repeatedly throughout your lifetime
- Reinfection can occur months or even weeks apart
- Previous infection may result in milder symptoms upon reinfection
- Being infected with one strain does not protect against others
- The virus can evolve into new strains that sidestep existing immunity
Young children are especially prone to repeat infections because they are frequently exposed. Even brief immunity decay allows reinfection from the multiple norovirus strains circulating.
What’s the difference between norovirus and the stomach flu?
Norovirus is sometimes referred to as “stomach flu” or “food poisoning,” but it is not actually related to influenza viruses that cause the flu.
Key differences between norovirus and the flu include:
| Norovirus | Influenza (Flu) |
|---|---|
| Highly contagious virus that causes vomiting and diarrhea | Contagious respiratory illness causes fever, cough, sore throat, runny nose |
| Spread by contaminated food or surfaces | Spread through respiratory droplets when coughing and sneezing |
| Sudden onset nausea, vomiting, diarrhea | Gradual onset fever, chills, muscle aches, fatigue |
| Typically resolves in 1-3 days | Symptoms last about 1-2 weeks |
Despite some overlapping symptoms like fever and fatigue, the two illnesses have distinct causes and transmission methods. Only influenza viruses cause true influenza. The “stomach flu” misnomer for norovirus lead to some confusion between the two.
When to see a doctor for norovirus
For otherwise healthy adults, norovirus usually resolves on its own without medical intervention. However, you should contact your doctor if you experience:
- Bloody or black stools
- Persistent vomiting for more than 24 hours
- Dehydration symptoms like infrequent urination, dry mouth, dizziness
- Fever over 102 F
- Severe abdominal or rectal pain
- Symptoms lasting longer than 3 days
Infants, young children, the elderly, and people with weakened immune systems should see a doctor right away if they have severe vomiting, diarrhea, or dehydration. IV fluids and electrolyte balancing may be needed.
Conclusion
Norovirus is a highly infectious virus that often causes outbreaks of acute gastrointestinal illness. Learning to recognize the most common signs and symptoms of norovirus can help you identify if you may have contracted it. Key symptoms include nausea, vomiting, diarrhea, and stomach cramps. While unpleasant, norovirus infection is temporary and most people recover fully within a few days. Paying close attention to hand hygiene and food safety practices can help prevent the spread of this virus.