Norovirus Facts

Making norovirus transmission understandable to those who are afraid of vomiting

(c) 2009 Anna S. Christie & Alvin J.V. Bois-Bonifacio


Norovirus: The most recent term for all “Norwalk-like viruses”
Stomach flu: Norovirus. Flu is a misnomer, as these viruses are not and never were influenza or “flu.” 
Stomach viruses: Noroviruses
Winter viruses: Noroviruses
Stomach bugs: Noroviruses (there are no actual “bugs”)
Winter vomiting flu: Noroviruses
Gastroenteritis: An illness of the gastro-intestinal tract that involves vomiting and diarrhea – these symptoms may be caused by Noroviruses or by bacteria. Hence, “viral gastroenteritis” or “bacterial gastroenteritis”. Bacterial gastroenteritis is not contagious. Edit Feb 19, 2021: “In some cases, the bacteria may be transmitted directly from one person to another, but they are typically spread through contaminated food and water.” [2]
Caliciviruses: Noroviruses (since they belong to the family of calicivirus)
NLVs: Norwalk-like viruses, now called Noroviruses


Noroviruses (genus Norovirus, family Caliciviridae) are a group of related, single-stranded RNA, non-enveloped viruses that cause acute gastroenteritis in humans. Norovirus was recently approved as the official genus name for the group of viruses provisionally described as “Norwalk-like viruses” (NLV). Currently, human Noroviruses belong to one of three Norovirus genogroups (GI, GII, or GIV), each of which is further divided into >25 genetic clusters.

How it works

  • You ingest (swallow) the virus by viral particles from feces or vomit entering your mouth. The virus incubates for 24-48 hours after ingestion, depending partially on how many viral particles you ingest. Noroviruses are particularly contagious because it only takes about a hundred of them to make you sick.
  • In your small intestine, the virus begins to multiply. The lining of your small intestine and/or your stomach will have appropriate attachments for the virus. It attaches itself and releases its genome (bio genes). Those genes shut down the cell and start taking control in order to make more viruses. Your cells are like a factory for the virus replicating.
  • Your cells then “explode” or lyse. Then it keeps going to more cells and so on.
  • While this is happening your immune response recognizes that cells are dying and T-cells allow your body to mount an immune response against it. They go to B-cells and produce antibodies. The antibodies travel to the small intestine and inactivate the virus.
  • The vomiting and even the diarrhea is a secondary response. It’s your body’s way, evolutionarily, to respond to an infection. It doesn’t actually do much to help you – the virus needs to run its course until it’s killed off by your immune system. Vomiting once or twice will help you feel better. But there is no need to “get the virus out of there” by vomiting more as it’s not only in your stomach – it’s in your intestinal tract as well.
  • The brain may allow you to “not vomit” if you convince it to. While this is not harmful when infected with Norovirus, it can be if you’ve ingested a chemical poison.
 It will certainly increase the length of time you suffer with Norovirus. 


Noroviruses die at 65 degrees Celsius or 150 degrees Fahrenheit. So the hot water cycle on your washing machine is PLENTY hot enough. So is the dryer!
Cooked food is normally much hotter – up to 74 degrees Celsius. Note that you cannot possibly wash your hands with water this hot (it will scald you) – so there is no need to make the tap run as hot as you can “stand it.” Soap and warm water washes the viral particles down the sink. The virus may survive freezing.

Incubation Period

24-48 hours after ingestion of the virus. Symptoms have been known to appear as early as 12 hours. It all depends on how much you’ve ingested.

When is it contagious?

Once the virus has been ingested and is incubating, it is possible to shed it through stool, without yet showing symptoms – but probably only for a few hours. One’s stool is contagious long after you get well. This is one reason why the virus is so highly contagious – people don’t know they have it, or think they’re over it, yet they spread it to others through poor hygiene (not washing their hands after defecating, then touching others or touching surfaces).

 Norovirus can live up to three weeks on surfaces, but after 9 days it’s normally not enough to make anyone sick. 

People are contagious for at least 24 hours after the symptoms disappear. There have been virus particles found in the stool samples of people who have been infected some time after this as well, however it is not known whether enough viral particles are secreted in order to infect someone else. (There are too many variables at this point: strength of the virus, number of particles, and strength of others’ immune systems.)

The person who had the virus becomes immune to this year’s particular strain and secretes antibodies with the virus so it isn’t contagious anymore to him, even though it is highly contagious to others.

 This could mean that if your spouse had the virus in October but you didn’t, in January he could bring it home and give it to you without ever being sick himself. 


Norovirus is transmitted through the fecal-oral (feces meaning “stool” and oral meaning “mouth”) route. This means you have to “swallow” the virus particles contained in the feces or vomit of someone who has the virus. “Swallow” means to ingest it into your gastro-intestinal system which is through your mouth. You bite your nails, you lick your fingers, or you contaminate that hotdog bun with your hand and then eat it. It’s also possible that a food-handler with Norovirus touches your food (that isn’t cooked) with dirty hands and then you eat it. This is one form of “food poisoning.” You may contract Norovirus through uncooked shellfish. Raw sewage finds its way into the ocean and into the shellfish – mainly those eaten raw or steamed – oysters, mussels, clams.

When someone vomits outside of a closed-in room (such as a bathroom) the act of vomiting produces a mist or spray that can send airborne particles into the mouths and noses of anyone nearby. As well, vomit particles may land on all surfaces in a bathroom such as flusher handles, taps, counters, light switches, even toothbrushes or cups. These are highly contagious. Similarly, diapers and clothing with fecal matter are highly contagious. Cleanup immediately all surfaces with a bleach solution of 1 Tablespoon of bleach to each litre or quart of water. The bleach solution needs to stay on the surface you’re cleaning for two or more minutes in order to work. Wear a mask if you’re caring for someone who is vomiting next to you.

The virus can be active outside a host (person) on surfaces such as counters, toilets, faucets, doorknobs, switches, etc. It is unknown exactly how long the virus can live on such surfaces, as this depends on the number of viral particles (microscopic or visible poop?), temperature, and the nature of the environment. Remember that you cannot catch it by just touching a doorknob. You would have to put your hand into your mouth. Therefore, hand-washing is imperative to prevention of transmission.

The main reason for all Norovirus outbreaks is poor hygiene, i.e., people defecating and not washing hands afterward, then contaminating surfaces or foods. Note: Alcohol-based hand gels do not all kill norovirus. Check the packaging. Anything with .13% benzalkonium chloride will do the trick.


The simplest, easiest and cheapest way to kill Norovirus on surfaces is with a chlorine bleach solution of 1 Tablespoon of bleach to 1 litre or quart of water (three times the amount needed for sanitizing surfaces). If you want to go crazy overkill, use TWO Tablespoons of bleach in your quart of water. That’s six times as much as you need. Never use straight bleach or even half and half bleach and water. A stronger mixture only wastes bleach and destroys the ecosystem – it doesn’t kill the virus any better. As well, the fumes and toxicity of bleach can make people in your household sick, especially over time. Mix it properly, spray it on, leave it for 2 minutes and gently wipe it off. 

Proper Hand washing Technique

Hand washing is the best way to prevent spreading and catching a Norovirus. Hands should be washed in the following way:

  • Use warm water, never hot
  • Use a mild soap. Antibacterial soap has no effect, as Norovirus is not a bacteria.
  • Wash hands for at least 20 seconds (you can sing the ABC song all the way through)
  • Rub palms, backs of hands, knuckles to palms, webbing of fingers, thumbs, wrists
  • Do not scrub harshly, use harsh soaps or chemicals or extremely hot water – this will destroy your skin leaving more pockets for the viral particles to attach to. Similarly, never wash your hands with bleach or a chemical not meant for hands.
  • Rinse well. You are washing the virus down the sink; you are not “killing” it.
  • Turn off taps with paper towel, and use paper towel to open doors, and then throw out the paper towel.
 Wash hands after using the rest room, and before eating – about 5 to 10 times a day.

It is impossible to get infected by Norovirus in any of these ways: 

1. Being “near” someone who has it, including co-workers or friends

2. Being on a plane with people who have it

3. Breathing the same air as someone who has it

4. Being in the same building as someone who has it

5. Walking past a pool of vomit on the floor, road or sidewalk

6. Having sexual relations with an infected person

7. Having a cut in your skin

8. Sitting on a toilet seat, or catching it through your rectum or genitalia 
9. Kissing someone who is not yet showing symptoms (Note: it may be possible to catch it from someone who has recently vomited by kissing them, as viral particles may be in their mouth from vomitus. But there is no evidence that the virus is transmitted through saliva, even though it may be detected in saliva.)

10. Sharing cups or utensils with someone who has the virus but isn’t showing symptoms (Note: It’s not recommend that you share drinks or utensils with someone anyway. Many other diseases can be transmitted this way – and some are more serious than Norovirus. However if you have shared a cup or fork with someone, then find out later that they have subsequently developed symptoms of a Norovirus, there is no need to fear.)

Is it airborne?

Norovirus is not airborne in the strictest sense of the word. Some news reports and even family doctors mistakenly report that it is, probably because it’s possible for airborne vomitus droplets to infect others. So if you’re standing near someone who vomits, the airborne “spray” from the vomit splashing will contain millions of viral particles and may infect you as you breathe them in and swallow them. This is not the same thing as a technically “airborne virus”. You cannot catch it from breathing the air of an infected person, going to their home, or working near them.

If your doctor or any other source tells you it is airborne in the sense that one can catch it by only breathing air, please ask them exactly what they mean, how they think the virus is transmitted, a technical/scientific source for their claims and the technical virology in writing that is contrary to what the world-renowned Center for Disease Control reports and claims. 


Rotavirus is a form of Norovirus that children usually get. To make a lot of technical facts quite simple, you don’t need to worry about rotaviruses. 


1) There is now a vaccine for rotavirus so vaccinated children can’t get it.
2) Adults will rarely if ever vomit from rotavirus infections, and
3) You can’t prevent the spread of them anyway. It’s just too contagious. Even if children wash their hands frequently, they commonly put their hands in their mouth and they’re not very good at washing up. Children can easily spread this virus. 


The Norovirus’s genetic profile changes often, meaning the proteins on its outside shell change constantly. Scientists are very close to developing a vaccine for it, and there is already a vaccine for rotavirus. As of 2019, four independent researchers are working to develop a vaccine, aided by the Bill and Linda Gates Foundation. It may still be several years before we see it in use. Noroviruses account for 50,000 deaths of children annually, most in developing countries.

Blood-Type Immunity

There is some good evidence that people with B or AB blood types are immune to noroviruses. By “immune” I mean that the evidence actually points to them being asymptomatic (not having any, or very mild symptoms). [1]


Noroviruses are normally quite unpleasant, but not dangerous to otherwise healthy adults. Children, the elderly or those with compromised health otherwise may be at risk for dehydration. 

CHILDREN: Follow the advice of a doctor or pediatrician only. Do not take advice from this or any other website. Dehydration in children can be fatal and it’s easy for kids to get dehydrated. 

HEALTHY ADULTS: If you are not vomiting, but have diarrhoea, ensure you are well hydrated at all times. If you are vomiting several times in a row try not to take anything by mouth for 2 hours and see if the vomiting stops. If vomiting stops then begin with very small sips of water every 10 minutes, or give a few ice chips. If the water does not stay down, try waiting again for an hour or so before sipping water or ice chips.  If vomiting continues despite withholding food & fluids, be on the alert for signs of dehydration and seek medical attention immediately. Dehydration can be fatal. If in doubt, go to an emergency room at once. Once you can keep water down, begin administering a fluid that will replace electrolytes such as Gatorade. 

ELDERLY/ILL PERSONS: Consult with a doctor. Don’t follow the advice of this, or any other website.

Always consult your doctor for treatment if you are concerned. Do not attempt to diagnose and/or treat any illness with information from this website or anywhere on the internet.


If you don’t put your hands in your mouth, don’t eat uncooked foods prepared in a restaurant, don’t stand beside someone who’s vomiting and don’t eat raw or steamed shellfish it is impossible to contract a Norovirus. Ensuring that your hands are properly washed before eating ensures that you will not catch it as well. There is no need to fear if you hear that someone at work or a friend you’ve visited has come down with the virus. You can’t catch it by simply being near someone who has it. 

No matter how much of an “outbreak” of the virus is in your geographic area, you are at no greater risk of catching it than if only one person has it. Good hygiene will ensure you are safe.

Research: Alvin J.V. Bois-Bonifacio (University of British Columbia)
Author: Anna S. Christie

[1] Source: Toronto Mt. Sinai Department of Microbiology
The information on this page, while derived independently, is in accordance with the information from the CDC (Center for Disease Control) in Atlanta.

[2] Source: (Sourced February 19, 2021)

© 2009 Anna S. Christie