Norovirus, often called the “winter vomiting disease,” is spreading quickly across the United States, with cases rising sharply as the colder season unfolds. Recent data from the Centers for Disease Control and Prevention (CDC) and wastewater monitoring systems show a clear national uptick, once again putting public health officials on alert.

While most people recover within a few days, norovirus can be dangerous for older adults, young children, and those with weakened immune systems. As US infection rates climb, understanding how the virus spreads, what symptoms to watch for, and how to stay protected has become essential.

What is norovirus, and why is it rising now?

Norovirus is a highly contagious virus that causes acute gastroenteritis, leading to sudden vomiting, diarrhea, stomach pain, and dehydration. It spreads easily through contaminated food, surfaces, and close contact with infected individuals. Because it thrives in cooler conditions and in close-contact environments, outbreaks are especially common in the fall and winter months.

This seasonal pattern explains why the United States is currently experiencing a surge. Cold weather pushes people indoors, increasing shared touchpoints and reducing ventilation—two ideal conditions for rapid norovirus transmission.

Norovirus also has an unusually long window of infectiousness. Even after a person feels better, they can continue transmitting the virus for up to two weeks. This prolonged shedding is one of the reasons outbreaks often spread faster than expected.

What symptoms does norovirus cause?

Norovirus symptoms tend to appear suddenly. Most infected individuals experience:

• Nausea
• Vomiting
• Diarrhea
• Stomach cramps
• Fever
• Headache
• Body aches

Symptoms typically start 12–48 hours after exposure. Children are more likely to vomit, while adults tend to experience more severe diarrhea. The most common medical concern is dehydration, especially among older adults and young children.

How widespread is the current norovirus surge in the US?

The United States is experiencing a notable rise in norovirus positivity rates. According to recent CDC data, 14 percent of norovirus tests are now returning positive—double the rate recorded just three months ago, when positivity stood at around 7 percent. More than 2,700 diagnostic tests were conducted in a recent week alone, meaning roughly 380 infections were confirmed during that period.

Annual burden

Norovirus causes:

• Approximately 2,500 outbreaks occur in the US each year
• More than 100,000 hospitalizations
• About 900 deaths annually

These numbers make norovirus one of the most common and costly causes of acute gastroenteritis in the country.

Who is most at risk of severe infection?

Although norovirus affects people of all ages, some groups face higher risks:

• Adults aged 65 and older
• Young children
• Individuals with compromised or weakened immune systems

Older adults remain the most likely to be hospitalized or die from norovirus-related complications, primarily due to dehydration or underlying medical conditions.

Long-term care facilities, assisted living centers, and daycare environments often experience clusters of infections because transmission occurs rapidly in shared spaces.

What wastewater data reveals about the current surge

WastewaterSCAN, a national virus-tracking program led by Stanford University, shows that norovirus levels in wastewater have climbed 69 percent nationwide since October. This makes the virus one of the most consistently detected pathogens in the network’s winter surveillance.

States reporting especially sharp increases include:

• Louisiana
• Michigan
• Indiana

“Right now, we’re in the high category for norovirus at the national level,” said Amanda Bidwell, scientific program manager at WastewaterSCAN, in an interview with NBC News.

Although levels are elevated, they remain lower than last winter’s peak. Bidwell added that norovirus tends to follow a clear seasonal pattern, but it is too early to predict the height of this year’s surge.

How does norovirus spread so easily?

One reason norovirus outbreaks are difficult to control is their resilience. The virus survives on surfaces for days, spreads through microscopic particles in vomit or fecal matter, and resists many common disinfectants.

Key transmission routes include:

• Direct contact with an infected person
• Touching contaminated surfaces and then touching the mouth
• Eating contaminated food (especially raw produce or shellfish)
• Aerosolized viral particles are released during vomiting

Even after recovering, a person can spread norovirus for up to two weeks. This long window of contagiousness often leads to recurring outbreaks in schools, cruise ships, restaurants, and healthcare facilities.

How to protect yourself from norovirus

Public health experts recommend simple but effective preventive steps:

Wash hands properly

Scrubbing hands with soap and water for at least 20 seconds remains the most effective defense. Alcohol-based sanitizers do not reliably kill norovirus.

Disinfect high-touch surfaces

Use bleach-based cleaners—one of the few disinfectants proven to inactivate norovirus.

Avoid preparing food while sick

People infected with norovirus should not cook for others for at least 48 hours after symptoms resolve.

Practice safe food handling

• Cook shellfish thoroughly
• Rinse produce well
• Avoid raw or undercooked foods during peak season

Stay hydrated

Frequent vomiting and diarrhea can cause dehydration quickly, especially in vulnerable groups. Oral rehydration solutions can help restore electrolytes.

Why this surge matters now

The rise in norovirus cases comes at a time when US hospitals are already preparing for increases in influenza, RSV, and COVID-19 as winter begins. A large norovirus wave could further strain emergency departments, especially if outbreaks hit nursing homes or pediatric facilities.

Historically, norovirus peaks between December and March. The earlier-than-usual climb this year may indicate a longer or more intense season ahead.

TL;DR: What to know about the US norovirus spike

• Norovirus positivity has doubled from 7% to 14% in recent months.
• Wastewater data shows a 69% national rise since October.
• Older adults, children, and immunocompromised people face the highest risks.
• The virus spreads easily and remains contagious up to two weeks after recovery.
• Handwashing, surface disinfection, and food safety are the most reliable protections.