Norovirus and flu (influenza) are often mistaken for one another, but they are two very different illnesses. What could be fueling the confusion is that norovirus is often referred to as the stomach flu – but, in fact, there is no such thing as stomach flu.
You see, the flu is a condition that affects the respiratory system. When you’re fighting the flu, your immune system is weakened. As a result, you are at a higher risk of catching other illnesses, such as norovirus. That’s oftentimes people associate gastrointestinal symptoms with the flu, but the two are completely different conditions.
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Norovirus is a highly contagious virus that does not have a cure and generally must run its course through your body. The resulting symptoms include vomiting, diarrhea, and abdominal cramping. Only rarely will norovirus will cause a fever – unlike the flu. Norovirus is also very quick to pass – typically, no more than 48 hours. Therefore, if you are still ill after a day or two, most likely, it is not norovirus, but something else.
Here we will explain the differences and similarities between influenza and norovirus to help you better understand each unique illness.
Norovirus vs. flu: Global trends
Norovirus is the leading cause of gastroenteritis (inflammation of the stomach, intestines, or both). In developed countries, cases of norovirus are one in five, and in developing countries they are one in six. In developing countries, there are more bacteria and other pathogens that can result in gastroenteritis, meaning there’s generally less norovirus cases.
Although the influenza season this past year was quite mild, the flu affects people worldwide and can even be fatal, especially among children, older adults, and those with weakened immune systems. Different parts of the world may experience different strains of influenza – the most common in North America this year were H1N1 and influenza B strains.
Table: Differences between norovirus and flu (influenza)
| Norovirus (“stomach flu”) | Influenza (flu) | |
|---|---|---|
| Cause | Virus that affects the stomach and intestines | Virus that affects the respiratory system |
| How common is it? | 23 million cases annually | Five to 20 percent of the U.S. population is affected annually |
| Symptoms | Nausea, vomiting, diarrhea, abdominal cramps Sometimes, a low-grade fever and chills | Fever, headache, sore throat, cough, body aches, congestion Vomiting and diarrhea – less common in adults but seen in children |
| Duration | 24 to 72 hours | Three to seven days, sometimes longer |
| Severity | Rarely causes severe complications Biggest complication is dehydration | Can cause complications in children, seniors, pregnant women, and those with weakened immune systems Sometimes can be fatal |
| Prevention | No vaccine is available, patients should wait at least 48 hours from their last bout of diarrhea or vomit before preparing food and being close to others Practice proper hygiene, frequently wash hands, don’t share food, drinks, etc. | Get the annual vaccine, use proper hygiene and hand-washing techniques, avoid those who are sick, cover your cough and sneeze |
Norovirus vs. flu (influenza) symptoms and complications
Here is a table that outlines the symptoms of both norovirus and influenza.
| Type of symptoms | Norovirus | Influenza |
|---|---|---|
| Digestive symptoms | Nausea, stomach cramps, vomiting, diarrhea | Nausea, vomiting, diarrhea |
| Respiratory symptoms | None | Cough, sore throat, runny or stuffy nose |
| Other symptoms | Fever, chills, muscle aches, fatigue | Fever, headache, body ache, chills fatigue |
A generally healthy person will bounce back from the flu within a few days, but in high-risk groups – children, seniors, pregnant women, and those with weakened immune systems – complications may arise.
Some complications from the flu are pneumonia, bronchitis, sinus, and ear infection, and in rare cases the flu can even be fatal. The flu can be worse in individuals with asthma or congestive heart failure as well.
The main complication resulting from norovirus is dehydration, and that is why it’s so important to stay hydrated during this time. Signs and symptoms of dehydration are fatigue, dry mouth, dizziness, and decreased urine output.
Norovirus vs. flu (influenza) transmission
The flu is spread through coughing and sneezing from an infected person. A cough or sneeze has the ability to pass on germs and the virus up to six feet away. These infected droplets can land on people around you and enter the lungs with an inhale.
Influenza can also be transmitted from contaminated surfaces and objects, meaning if you touch a surface that has been touched by an infected person you can catch influenza. This is why it’s so important to frequently and properly wash your hands. If soap and water is not available, an alcohol-based sanitizer can help kill germs, too.
Norovirus is transmitted through the consumption of contaminated food or water, touching surfaces that are contaminated, or being around someone who is infected. A person with norovirus is most contagious when sick and even a few days after the symptoms have subsided.
Norovirus outbreaks commonly occur in settings where there are many people in close quarters, such as cruise ships, daycare centers, retirement homes, dining halls, school dormitories, and hospitals.
Norovirus vs. flu (influenza) treatment and prevention
There is no cure or specific treatment for norovirus. Your best bet is to rest and drink plenty of fluids in order to prevent dehydration.
Influenza often does not require treatment as well and will pass on its own. Some treatment methods are to aid in symptom relief, such as taking painkillers and sticking to a bland diet. In some cases, your doctor will prescribe antiviral drugs. You should also avoid contact with others and get as much rest as possible.
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Prevention of influenza can be easily done with a flu shot along with proper hygiene and caution around sick people. Norovirus is similar in the sense that you should avoid sick people, but unfortunately there is no vaccine available. Avoid sharing beverages, food, utensils, and other objects, and always wash your hands.
Norovirus can also be prevented by properly washing, preparing, and storing food. If you are sick, avoid making meals for others.
By following these prevention tips, you can better protect yourself from norovirus and influenza.
Emily Lunardo studied medical sociology at York University with a strong focus on the social determinants of health and mental illness. She is a registered Zumba instructor, as well as a Canfit Pro trainer, who teaches fitness classes on a weekly basis. Emily practices healthy habits in her own life as well as helps others with their own personal health goals. Emily joined Bel Marra Health as a health writer in 2013.
