When Should I Worry About...

How to Avoid Norovirus: The U.S.'s Most Prevalent Stomach Bug

July 2, 2024 - Josh Davis

Norovirus is one tough virus — able to survive for weeks outside of the body in freezing or hot temperatures. And hand sanitizer? Child's play to norovirus, which isn't killed by alcohol-based disinfectants like other viruses and bacteria are.

Once norovirus infects a host, it's able to replicate within days and shed billions of virus particles that can either become airborne or live on in the environment, susceptible to getting picked up. Once a person recovers, they may still spread the virus for up to four weeks. In the end, it takes only around 100 of those viral particles to infect a new host, starting the process anew.

Because norovirus is so hardy, it's easy to see why in close-quarter settings like schools, restaurants, health care facilities and — perhaps most notoriously — cruise ships, the virus can "spread like wildfire," according to Dr. Cesar Arias, chief of the infectious diseases division at Houston Methodist.

However, despite its considerable proficiency infecting, shedding and spreading, norovirus can be avoided and prevented with proper steps and strategies.

What is norovirus and what isn't?

Norovirus is a highly contagious virus that primarily affects the lining of some portions of the intestine and is the leading cause of vomiting, diarrhea and foodborne illness in the U.S. It was originally named Norwalk virus after the Ohio town where it was first identified following an outbreak in 1968, and you'll sometimes see it referred that way even today.

What norovirus isn't, however, is the stomach flu — despite what you might read or hear to the contrary. What's more, lots of viruses, like influenza and some others you might not expect, can cause similar gastrointestinal symptoms, according to Dr. Arias.

"Stomach flu is a very nonspecific term that refers to any multitude of viruses that may involve the gastrointestinal tract as part of a large constellation of symptoms," says Dr. Arias. "The most prominent symptoms are vomiting, diarrhea, and abdominal discomfort (including pain), but several bacteria and viruses, including respiratory viruses, can affect the gastrointestinal tract and present similar symptoms."

"COVID-19, for example, sometimes presents with gastrointestinal symptoms, and potentially influenza can also cause diarrhea during its acute illness," he says.

The signs and symptoms of norovirus include:

  • Sudden or unexpected vomiting that's not bloody (red)
  • Diarrhea that's also usually not bloody
  • Fever, stomach pain, and malaise (generally feeling ill)


How do you know if it's norovirus, flu, bacteria or another GI bug?

"Without consulting a medical provider, it's actually very difficult to tell what kind of pathogen you may have," says. Dr. Arias. "There are certain clinical and epidemiological characteristics (that is, specific exposures) that can help identify the organism, like the appearance of your stool, whether you have fever, if you present with vomiting, or the time between when you think you got infected and when you started developing symptoms."

For example, food that's contaminated with certain types of harmful bacteria can almost immediately induce vomiting, according to Dr. Arias, whereas norovirus typically has an incubation period (the time between exposure and onset of symptoms) from 12 to 48 hours.

(Related: Food Poisoning: How to Know If You Have It & How Long It Can Last)

How does norovirus spread?

"Norovirus can be transmitted very easily and by many routes, mainly in close-contact communities," says Dr. Arias. "Cruise ships is one of those settings, but it's also common for norovirus to spread in schools, hospitals, military populations, athletic teams, prisons, local water supplies and during natural disasters."

The three main routes Dr. Arias mentions are:

  • Fecal-oral transmission
  • Contaminated foods
  • Airborne droplets from vomit


By understanding how norovirus spreads, we can take steps to prevent outbreaks and avoid infection.

Fecal-oral route

For starters, let's address the elephant in the room — the fecal-oral route. The route, where feces particles pass from an infected person to another's mouth, is actually a fairly normal occurrence, according to Dr. Arias.

"Believe it or not, the fecal-oral route of disease transmission is a very human occurrence," says Dr. Arias. "As humans, we are colonized with feces no matter how clean we think we are, because that's simply part of who we are. Those germs get onto our hands very easily, so even the smallest touch or contact happens more often than not."

In reality, the fecal-oral route is much more nuanced than simply not washing your hands. Five distinct modes of fecal-oral disease transmission exist that, luckily, can be controlled:

  1. Flies that touch feces then land on food
  2. Fields where fecal matter contaminates the soil and crops
  3. Fluids when the water supply has been contaminated
  4. Fingers from unwashed hands when preparing food
  5. Food that is contaminated with fecal particles


Contaminated foods

Certain foods, including raw leafy greens, fruits and shellfish have all been linked to previous norovirus outbreaks, says Dr. Arias. In total, norovirus accounts for more than half of all foodborne illnesses in the U.S.

(Related: Is the 5-Second Rule Actually True?)

Airborne droplets

The third and final route of norovirus occurs when tiny droplets of vomit become airborne, carrying with it viral particles that can go on to infect nearby individuals.

Should norovirus deter you from going on a cruise ship?

Cruise ships have a notoriety for norovirus outbreaks, particularly in the media. But in reality, only 1% of all reported norovirus outbreaks occur on cruise ships, according to the CDC. That said, if an outbreak of diarrhea does occur on your out-at-sea vacation, norovirus is the underlying culprit more than 90 percent of the time.

So should you forgo your cruise in lieu of a potential norovirus outbreak? Probably not, but Dr. Arias says would-be passengers should be aware of the risk.

"Cruises can be lots of fun, but they're definitely settings where infectious agents like norovirus can be transmitted more easily," says Dr. Arias. "If you have an infection, particularly a viral one, it's going to spread faster in a closed environment like a cruise where you don't have anywhere to go."

(Related: 5 Summertime Health Hazards to Avoid)

How do you treat norovirus?

As bad as it is, norovirus at least usually resolves on its own in a few days' time in most people. But younger children and older adults may have more severe symptoms or complications.

"The most common complications we see are when patients aspirate (breathe in) vomit and end up with stomach contents in their lungs, or dehydration from diarrhea," says Dr. Arias. "Dehydration can be particularly dangerous for immunocompromised patients."

In rarer cases, says Dr. Arias, norovirus can cause benign seizures if a patient has high fever as a result of infection. Even more rare is encephalitis — when the brain becomes inflamed — a rare but serious complication that can lead to death.

"The important thing is to know when your symptoms are severe enough to seek medical attention," says Dr. Arias. "This will depend on who you are, your age, and what kind of medical conditions you have, such as if you're undergoing cancer treatment, are immunocompromised or have had a solid organ transplant. Norovirus can worsen these conditions and potentially make you very sick."

(Related: PODCAST: Is Water Enough to Keep You Hydrated?)

How can you avoid getting norovirus?

Wash your hands often and well

"Washing your hands with soap is the best way to avoid getting norovirus," says Dr. Arias. "You really want to wash your hands thoroughly, making sure to wet your hands with clean water, cover all the surfaces of your hands with soap and lather your hands for at least 30 seconds. You don't need to overdo it, though."

When lathering, make sure to scrub between your fingers, under your nails, and the backs of your hands.

"Make sure to rinse your hands on both sides, dry your hands with a clean towel, and discard the towel without touching the faucet," he adds.

(Related: Washing Your Hands: Why It Matters)

Prepare your own food separately

If you can, Dr. Arias suggests preparing or getting your own food and to make sure the cutlery and dishes are treated properly with soap and water. Many dishwashers come with a "sanitize" function on them, which can further help to decrease the line of transmission.

Disinfect surfaces with bleach

The CDC recommends using a chlorine bleach solution of 5 to 25 tablespoons of bleach per gallon of water. Leave the disinfectant on the area for at least five minutes and clean the area again with soap and hot water. Don't forget to wash your hands afterwards.

Use a restroom no one else will use

"If you have norovirus, you're likely to have spread it outside of the toilet, so all the surfaces in the bathroom are going to be contaminated," says Dr. Arias. "Closing the lid before you flush is not going to make a difference. The ideal situation would be that you use one restroom only and no one else uses it."

"The more you contain your secretions, the more you can prevent norovirus from infecting others," he adds.

Stay up-to-date
By signing up, you will receive our newsletter with articles, videos, health tips and more.
Please Enter Email
Please Enter Valid Email
Categories: When Should I Worry About...