Norovirus, also known as the “stomach flu” or “winter vomiting sickness,” is active in California and across the nation. But cleaning and disinfecting can help check its spread, experts say.

Precautions are crucial because the virus is highly infectious and there’s no real treatment for it, the Centers for Disease Control and Prevention said.

From Aug. 1 through Nov. 13, 153 norovirus outbreaks were reported in 14 states. The agency defines individual outbreaks as two or more similar illnesses resulting from a suspected or laboratory-confirmed cases of norovirus.

While California is not one of the reporting states, CDC data shows a sharp increase in positive norovirus tests throughout the month of November for the entire western United States.

The California Norovirus Laboratory Network has confirmed 32 cases in the state through laboratory testing in 2025, the California Department of Public Health said. The state health department reviews data collected by WastewaterSCAN to check “overall trends in the community.”

Here’s what to know:

What is norovirus? Is it the same as the flu?

Norovirus is a “very contagious” disease that causes vomiting, diarrhea and stomach cramps, according to the California Department of Public Health.

The virus inflicts acute gastroenteritis — inflammation of the stomach or intestines — on people of all ages in the United States, the CDC said.

Even though it’s often called the “stomach flu,” norovirus is not related to the flu, which comes from the influenza virus, the agency said.

Every year, there are about 2,500 reported norovirus outbreaks across the country, with surges most common from November to April.

On average each year, the highly contagious virus causes 109,000 hospitalizations, 465,000 emergency department visits and 19 million to 21 million illnesses, according to CDC data.

Norovirus is the “leading cause of vomiting and diarrhea” and causes 58% of foodborne illnesses in the nation, the federal public health agency said.

How does the stomach bug spread?

Norovirus spreads easily from person to person, while infected individuals are experiencing symptoms, according to the California Department of Public Health.

Symptoms typically last one to three days, though someone can still be contagious up to two days after they feel better, according to the public health department’s website.

The virus disseminates from a person’s vomit and stool, spraying into the air or landing on nearby surfaces.

It can survive for weeks on unwashed objects, such as countertops, phones and doorknobs, the public health department said.

“You can get sick after touching or caring for someone who is sick,” the department said, “or after touching or eating something that is contaminated.”

The virus can spread very quickly in closed and crowded environments, including schools, child care centers, hospitals, nursing homes, jails and cruise ships, according to the state Public Health Department.

Here are the most common ways to catch norovirus, according to federal and state health officials:

—Touching, caring for or sharing food with a person infected with norovirus

—Eating or drinking something that has norovirus in it, including undercooked shellfish like oysters

—Touching a contaminated surface and then touching your mouth before washing your hands

—Sharing the toilet or bathroom with someone who is sick with norovirus

—Swallowing water that has norovirus in it, including water in swimming pools or other recreational areas

—Cleaning up vomit or diarrhea without wearing protective gear, such as gloves and a face mask.

“​Anyone can get norovirus, even if they’ve had it before,” the California Department of Public Health said.

Do you need to disinfect after norovirus?

“If you or someone in your household is sick with norovirus, it’s important to clean and disinfect areas where someone has vomited or had diarrhea,” the California Department of Public Health advised. “Cleaning with soap and water removes germs from surfaces, while disinfecting kills any remaining germs.”

You can use store-bought disinfectants to clean up after the stomach flu, but check the label to be sure it lists norovirus as one of the microorganisms it kills.

You also can check the federal Environmental Protection Agency registration and search for the number in the EPA’s List G – Registered Antimicrobial Products Effective Against Norovirus.

You also can mix your own bleach solution to disinfect after norovirus, the U.S. Department of Agriculture said. “Mix 5 to 25 tablespoons of household bleach in a gallon of water.”

Apply this solution only to hard or nonporous surfaces with a spray bottle or disposable mop, sponge or paper towel, the department said. Let it sit about five minutes before wiping.

“Give extra attention to disinfecting things that are commonly touched in the home, such as doorknobs, remote controls and handles,” the USDA said.

Be aware that many disinfectant wipes are not completely effective at killing norovirus, the agency said.

How do you clean up after norovirus?

Wear rubber or disposable gloves, the CDC said. Wipe the entire area with paper towels and throw them in a plastic trash bag.

The California Department of Public Health also suggests wearing a face mask.

After disinfecting, clean the entire area again with soap and water, the CDC said.

Be aware the virus may be aerosolized when someone vomits, meaning surfaces several feet away could be contaminated, the USDA said.

Throw away your gloves and mask when you’re done, the California Department of Public Health said. Then, take out the trash.

What about laundry?

“Using disposable gloves and a face mask, remove and wash all clothes and linens that may have vomit or poop on them,” the California Department of Public Health said. “Be careful to handle items without shaking them.”

Wash the items with detergent and hot water at the longest laundry cycle, then dry them on high heat, the CDC said. Wash your hands with soap and water after handling infected clothing.

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