How can you avoid norovirus (the stomach flu)?

Hand sanitizer doesn’t work well on this nasty bug. So how to dodge norovirus symptoms this season?

A person washing their hands with soap

The norovirus – a virus that’s the country’s leading cause of vomiting, diarrhea, and foodborne illness – is picking up steam again as the holidays arrive.

Recently the California Department of Public Health (CDPH) warned that norovirus — commonly known as the stomach flu — is “on the rise.”

As of Dec. 12, norovirus levels in wastewater in the U.S. West and South were labeled “medium” according to data linked on the department’s website, but were “high” in the U.S. Midwest and Northeast. As of Dec. 20, levels were high at the Sacramento Regional Wastewater Treatment Plant, as well as in San Francisco.

Norovirus is highly contagious, and it travels from person to person a bit differently than the respiratory viruses that cause flu, COVID and common colds. That can be both good and bad news.

Read more below to arm yourself with more understanding about norovirus symptoms and behavior — and how you can increase your chances of avoiding this bug.

What is norovirus?

Norovirus is one of several intestinal viruses that cause diarrhea, vomiting and gut cramps that can last for multiple days. Sometimes, this can lead to dangerous levels of dehydration.

When you hear about nasty outbreaks of stomach illness in places like cruise ships, day cares and senior facilities, it’s highly likely you’re hearing about norovirus. It’s sometimes even called “the cruise ship virus.” These are all places where people spend time close to each other, and where they usually eat and drink together from the same food source.

For many people, those conditions also happen during holiday gatherings.

How long do norovirus symptoms last?

Symptoms usually start 12 to 48 hours after contact with the virus, according to CDPH. A person may vomit and/or have diarrhea many times a day, with symptoms usually lasting 1 to 3 days.

How is norovirus treated?

There’s no specific treatment for norovirus, and it usually gets better on its own. There are things you can do to ease symptoms, such as resting and drinking extra liquids to help restore the fluids that you lose quickly during diarrhea and vomiting.

When symptoms are severe, health care providers may give intravenous (IV) fluids to treat severe dehydration.

No licensed antiviral therapy (such as Tamiflu) is currently available for norovirus. Some off-label agents are sometimes used for immunocompromised patients with weakened immune systems.

Norovirus symptoms, and when they’re an emergency

How does norovirus spread?

It sounds gross, but norovirus mainly spreads when vomit or particles of feces from an infected person get swallowed by an uninfected person. This can happen in several ways.

Foods and drinks: When people don’t wash their hands when making food, they are more likely to contaminate it.
Surfaces and objects: If your fingers then go into your mouth — or onto objects like a chewed pen — norovirus can go with them.
Physical contact: Shaking hands or caring for a member of your household who is sick can also spread the virus.

According to CDPH, a person is most contagious as soon as they start feeling sick until a few days after symptoms stop. However, they may still be contagious for two weeks or longer after feeling better.

Can you get norovirus by breathing it in?

Breathing in virus particles is not thought to be the primary way that norovirus spreads. It doesn’t invade your body by infecting cells inside your nose, mouth or airway like respiratory viruses. Instead, it infects your gut after reaching it with food or saliva.

Generally, it isn’t recommended to wear a mask in a crowded indoor place to avoid norovirus. However, it is possible that being near an infected person while they’re sick, or while cleaning up after them, could expose you to tiny droplets of vomit or feces that contain the virus. Theoretically, these can enter your mouth, so wearing a mask during clean-up can still be a good idea.

When to be concerned about diarrhea in your child

How contagious or spreadable is norovirus?

Norovirus is extremely contagious, with transmission characteristics that are above flu and COVID but less than measles.

Why is norovirus so contagious?

Armor, for one. Norovirus has an outer shell of protein that’s much tougher than the soft envelope of fat around viruses like the flu or the novel coronavirus (COVID).

This protects the norovirus from many things that could kill a lesser virus, such as:

Temperature swings: Noroviruses can live through temps as high as 145°F and as low as freezing, helping it survive food storage and prep.
Acidic conditions: Norovirus can survive exposure to stomach acid.
Cleaning products: Hand sanitizer doesn’t work well on norovirus. Neither do many common cleaning wipes or products, unless registered for killing norovirus.
Weather and physical contact: It can survive for days or weeks on doorknobs, countertops, phones and hard surfaces.

The amount of norovirus that it takes to cause illness is also remarkably low – as few as 18 to 1,000 viral particles. A single episode of vomiting contains enough virus to infect 150,000 people.

Cleaning, disinfecting and laundry during norovirus

How can I protect myself from norovirus?

For one, don’t eat food prepared by people who are sick or were sick recently. But that can be hard to control. So, you can also make sure that you clean your hands at key times, by washing them with soap and water for at least 20 seconds.

A simple rule could be: “Before putting something in my mouth, I make sure I’ve washed my hands first — especially in a group setting or around someone who’s sick.”

If you’re really concerned about norovirus, here are some examples of times you might want to be sure you wash your hands before eating:

At a shared meal, after serving dishes have made the rounds and you’ve loaded your plate.
While snacking, if using shared serving utensils at the appetizer table, or pouring drinks from a shared bottle.
After shaking hands when greeting someone at a gathering with food and drink.
At a restaurant, after touching shared items like a menu, or the serving utensils in a salad bar or buffet.
At the workplace, if you’re snacking while using a computer or other equipment.

If you can’t wash your hands before touching food and you’re very concerned about norovirus, you could also stick to eating with utensils only.

How best to kill norovirus when doing dishes?

Cleaning dishes and utensils in a dishwasher is the most reliable method to prevent norovirus spread. That is because the water typically reaches 140-160°F in the sanitizing cycle.

The blend of hot water and detergents used in dishwashers is sufficient to decontaminate dishware and eating utensils exposed to norovirus. No special precautions are needed beyond standard dishwashing practices.

Can I track norovirus levels?

Public health officials can look for trends and spikes by watching how much virus shows up at wastewater treatment plants in different communities, using tools such as the WastewaterSCAN program.

See searchable WastewaterSCAN data here

State and local health officials also track outbreaks of norovirus, which is when two or more people get sick from a common source. They may issue alerts through the news media and social media.