Norovirus is a highly contagious viral infection that causes your intestines to become inflamed. As a result of the inflammation, you’ll likely experience symptoms like diarrhea, vomiting, and stomach pain. Generally, these symptoms develop about 12 hours to two days after exposure to the virus. In most cases, symptoms go away on their own within three days as your body fights off the infection.¹

Keep in mind: while this condition is sometimes referred to as a stomach bug or the stomach flu, norovirus is not the same as influenza (flu) virus. But norovirus is very common. In fact, in the U.S., researchers estimate that the virus causes about 20 million cases of diarrhea and vomiting each year. That said, it’s important to understand the symptoms and know when to see medical attention.

Common Symptoms  

Norovirus is a common cause of gastroenteritis—which is a term to describe any type of inflammation in the stomach and intestines. As such, it’s common to experience symptoms that mainly affect your digestive tract—a tube that connects your mouth to your anus and includes organs like your esophagus, stomach, and intestines.

It’s worth noting that some people who contract norovirus don’t experience any symptoms at all. But they can still spread the infection to other people. Because the virus is so contagious, you can spread norovirus even before symptoms start and two days after your symptoms go away.

Diarrhea 

The most common symptom of norovirus is diarrhea. Researchers have found that diarrhea occurs in over 87% of all norovirus cases. Diarrhea causes loose, watery stools (poop). You may also feel a need to use the bathroom more often. Generally, this symptom will resolve on its own within three days. But it may take longer for people over 65 and toddlers or infants.

Nausea and Vomiting 

When you become exposed to norovirus, you can expect several bouts of nausea and vomiting. This means you feel sick to your stomach and may have to throw up. People with this infection tend to experience these symptoms multiple times a day, usually for one to three days. In one study, researchers found about 25.5% of those exposed to norovirus experience these symptoms.³ Children, those older than 65, or people with autoimmune conditions may experience symptoms longer.

Stomach Pain 

Another common sign of norovirus infection is stomach pain. This symptom usually happens when the lining of your stomach becomes inflamed. Your stomach pain may feel like severe or sharp cramping. 

Less Common Symptoms 

Alongside the digestive symptoms, norovirus can also cause other, less common issues in your body. These symptoms include a fever with a temperature over 100.4 degrees Fahrenheit, chills, headache, muscle aches, and joint pain. Some people might experience leukocytosis (high white blood cell count) and thrombocytopenia (a low level of platelets, a type of blood cell that helps form clots after injury) when they have norovirus.

Rare Symptoms  

Over time, norovirus-related vomiting and diarrhea may sometimes lead to fluid loss and dehydration. Being dehydrated can lead to serious consequences or even become fatal, especially if you’re very young, older than 65, or have another underlying health condition.

The typical signs of dehydration are:

• Urinating less frequently
• Sweating less than usual
• Very dark-colored urine
• Increased thirst
• Sore throat
• Dry mouth or dry skin
• Dizziness that worsens when you stand up
• Fatigue

Because those who have weakened immune systems tend to have symptoms for longer, dehydration can become even more severe among people who are immunocompromised. Serious complications of dehydration, such as confusion, fainting, lack of urination, elevated heart rate, rapid breathing, and shock, are medical emergencies that can occur in rare instances.⁴ Drinking water and increasing your fluid intake are important when you have norovirus.

Symptoms in Children   

Since this infection is highly contagious and spreads through close contact, norovirus is relatively common in infants, toddlers, and young children. Norovirus symptoms in children are similar to the symptom’s adults experience. If your child has norovirus, they may experience:

• Diarrhea
• Nausea and vomiting
• Headache and body pain
• Fever or chills
• Dry mouth or tongue
• Crying without producing tears
• Lack of diaper wetting for three or more hours
• Irritability or restlessness
• Excessive sleepiness or drowsiness

When to Contact a Healthcare Provider  

While most cases of norovirus infection resolve on their own, some cases can become very serious. In addition, potentially dangerous bacterial or viral infections can cause symptoms that are similar to norovirus symptoms. That said, knowing when to contact a healthcare provider—or call for emergency help—is critical.

In general, if you’ve had symptoms for longer than three days or are unable to hold down food or liquids, you should call your healthcare provider. If you or a loved one are experiencing severe symptoms of dehydration (such as fainting, lack of urination, and rapid breathing), it’s important to get medical care urgently.⁴

Questions to Ask Your Provider 

If you’ve gone to a hospital or clinic with norovirus symptoms, make sure to ask your healthcare provider the following:

• Can my diarrhea be due to another type of infection?
• Which tests can help me get a diagnosis for norovirus?
• What foods and drinks do you recommend to help me recover from the infection?
• Are there any medications I can take to reduce nausea?
• What can I do to avoid spreading my infection to others?

A Quick Review  

Norovirus is a highly contagious infection that causes inflammation of the digestive tract. Symptoms of this infection usually occur between 12 and 48 hours of exposure to the virus. If you contract this infection, it’s common to experience symptoms like diarrhea, nausea, and stomach pain. But norovirus can also cause symptoms like fever, chills, and dehydration. If you have symptoms for three or more days or are experiencing severe symptoms of dehydration, it’s best to see your healthcare provider immediately for medical support.  Medically reviewed by Jurairat J. Molina, MD (First seen in Health)