Signs and symptoms of norovirus infection include:

• Nausea
• Vomiting
• Abdominal pain or cramps
• Watery or loose diarrhea
• Malaise
• Low-grade fever
• Muscle pain

Signs and symptoms usually begin 12 to 48 hours after first exposure to the virus and last one to three days. You may continue to shed virus in your feces for up to two weeks after recovery. Viral shedding may last several weeks to several months if you have an underlying health condition.

Some people with norovirus infection may show no signs or symptoms. However, they are still contagious and can spread the virus to others.

Noroviruses are highly contagious and are shed in the feces of infected humans and animals. Methods of transmission include:

• Eating contaminated food
• Drinking contaminated water
• Touching your hand to your mouth after your hand has been in contact with a contaminated surface or object
• Being in close contact with a person who has a norovirus infection

Noroviruses are difficult to wipe out because they can withstand hot and cold temperatures as well as most disinfectants.

Risk factors for becoming infected with norovirus include:

• Eating in a place where food is handled with unsanitary procedures
• Attending preschool or a child care center
• Living in close quarters, such as in nursing homes
• Staying in hotels, resorts, cruise ships or other destinations with many people in close quarters
• Having contact with someone who has norovirus infection

For most people, norovirus infection clears up within a few days and isn't life-threatening. But in some people — especially children and older adults with compromised immune systems in hospitals or nursing homes — norovirus infection can cause severe dehydration, malnutrition and even death.

Warning signs of dehydration include:

• Fatigue
• Dry mouth and throat
• Listlessness
• Dizziness
• Decreased urine output

Children who are dehydrated may cry with few or no tears. They may also be unusually sleepy or fussy.