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This post was written by Dr. Thomas Wright, PPG - Infectious Disease.
Norovirus has earned the moniker “winter vomiting disease” because it causes a vomiting-predominant gastroenteritis that spreads from October to March. It can still cause severe watery diarrhea along with vomiting, which can cause severe dehydration and lead to over 100K hospitalizations in the US each year.
The 2025-2026 season is well underway, with news reports of an elementary school in Massachusetts shutting down and cruise ship outbreaks sickening hundreds so far this year. Norovirus can also circulate in hospitals and nursing homes, placing the most vulnerable at risk.
How is norovirus transmitted?
In each gram of stool, there are up to 10,000 – 100 billion viral particles. However, it only takes ingesting 100 viral particles to become ill with norovirus. Norovirus can also be shed from feces at lower amounts for 2 weeks or more after you recover symptomatically.
This viral infection is very stable in the environment; it resists freezing and heating, can survive common household disinfectants such as alcohol-based cleaners and can survive on surfaces for up to 2 weeks. Its resilience makes it very contagious and can spread in several ways, including via:
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Fecal-oral transmission of the virus occurs via ingestion of viral particles originating from stool.
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Airborne droplets containing viral particles released during vomiting can be inhaled by others.
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Fomite transmission of viral particles from surfaces such as countertops, tables, or other contaminated objects to hands, followed by hand-to-mouth contact.
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Consuming contaminated food or water, or eating fruits and vegetables that have come into contact with contaminated water.
When to seek medical attention
If you contract norovirus, a mild and brief illness usually develops 24-48 hours after ingesting contaminated food or water. Common symptoms include nausea, vomiting, diarrhea and abdominal (belly) pain. These may last 48-72 hours, but hospitalization is rare.
It’s crucial to stay hydrated, as dehydration due to severe vomiting and diarrhea can occur within a matter of hours. If you are unable to drink enough water to replace the fluids you lose, then you may need to seek medical attention for IV fluid hydration.
Adults who are immunocompromised or older adults are at risk for prolonged symptoms and at higher risk for dehydration. Signs of dehydration can look like:
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Headache
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Thirst
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Cramping
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Light-headedness
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Dry skin
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Dark yellow or orange shaded urine
In children, dehydration can present as crying without tears, fussiness or sleepiness.
How to prevent transmission
Wash your hands with soap and water. Alcohol-based hand sanitizers don’t entirely eliminate norovirus. Soap is more powerful than you may think. Its structure is made of two components: a water-loving head and a long, water-fearing tail. This lollipop-like structure squeezes itself into the protective membrane of viruses and bacteria, leading to the rupture and death of the microorganisms.
Handwashing with soap and water is the best way to prevent transmission of norovirus to yourself and to others. The Centers for Disease Control and Prevention (CDC) recommends these five steps for handwashing:
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Wet your hands with clean, running water (warm or cold), turn off the tap, and apply soap.
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Lather your hands by rubbing them together with the soap. Lather the backs of your hands, between your fingers and under your nails.
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Scrub your hands for at least 20 seconds.
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Rinse your hands well under clean, running water.
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Dry your hands using a clean towel or an air dryer.
The CDC also recommends using chlorine bleach solution to clean and disinfect surfaces and bathrooms. Leave bleach on for five minutes before cleaning with soap and water. Remember to wear gloves and eye protection, and to ensure adequate ventilation when using bleach products.
If you had diarrhea caused by norovirus, you should stay home for 2 to 3 days after your symptoms end before going back to work or school to help prevent the spread of the virus.
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