How is the stomach flu transmitted (norovirus and others)?
Answer: You catch the stomach flu when virus-infested feces, vomit, or nasal secretions get into your mouth. Norovirus can be present in saliva.
The stomach flu is highly contagious and is primarily spread through the fecal-oral route. Technically, you need to swallow the virus to get the illness. When a person has viral gastroenteritis, the viruses are present in their feces and vomit. If another person accidentally swallows a few of these viruses, they get sick. Anything that you put into your mouth that has the viruses on it, can make you sick. (Food, your fingers, pen cap, toothbrush, etc.)
Improper Hand Washing
The main reason these viruses spread like wildfire is thought to be improper hand washing. We aren’t washing our hands good enough after we go to the bathroom or change a diaper. Here are some examples of how the stomach flu can be spread by dirty hands. A person who is ill or contagious and uses the bathroom can leave some viruses on the faucet, flusher, toilet seat, or hand towel to wait for the next person. A restaurant or cafeteria worker who is contagious with a stomach virus, can start an outbreak by chopping lettuce with a microscopic fleck of feces under her fingernail. Diaper changing is another easy way to spread illnesses. Just think about all the things you touch after you change the baby's diaper BEFORE you wash your hands--especially if you have a kicking, twisting 1-year old. You touch the baby's clothes, the box of wipes, maybe a door knob, a light switch, your sleeves, and the faucet. A few of the viruses on your sleeve dry and fall onto your sandwich later that day. you are wondering where you went wrong. It is hard to do a perfect hand washing. So, if you or a family member actually has a stomach bug, I would recommend using a hand sanitizer that kills norovirus such as Clorox Hand Sanitizer Spray on your hands after you wash them in the sink. For more hand sanitizer suggestions, read this page. I would also recommend wearing disposable gloves to change a sick child's diaper and clean up.
Viruses are easily spread all over the house.
I know what you are thinking. The last time someone in your house got the stomach flu, you washed your hands till they bled and you still got sick. This is partly because when a person (especially a child) is sick with viral gastroenteritis, the vomit and diarrhea get a whole lot of other places besides hands. Their clothes get covered and perhaps the carpet and toys. When the viruses are all over the place like that, it is hard to prevent other people in the house from catching the illness. It is hard to clean up every microscopic spec of vomit. If the sick person is an adult who makes it to the toilet, you have a good chance of containing the virus. But when it is a child who vomits in the middle of the family room, it is very difficult. Make sure to read the page about cleaning products that kill norovirus including Clorox Hydrogen Peroxide Wipes. In addition, your clean laundry is NOT sterile. I have done experiments that show that there are still live bacteria in clean laundry even after washing on hot, with chlorine bleach, and 1.5 hours in a hot dryer. I imagine that some viruses would survive that as well. I would wash all sick laundry 2 times AND make sure to wear disposable gloves when transferring the laundry from the washer to the dryer.
Stomach flu viruses can be temporarily AIRBORNE!
Norovirus has also been shown to become temporarily airborne when a person vomits. This is most likely true for the other gastroenteritis viruses as well. In one study, a person vomited in a hotel dining room. People eating at other tables all over the room got sick which could not be explained by direct contact. People at closer tables were more likely to be sick than people whose tables were farther away1. When the virus particles settle out of the air, you have a nice light coating of virus all over the room. So, if your child vomits in the middle of the family room carpet, it is very easy for everyone to be exposed. People can breath in and swallow the temporarily airborne viruses or touch contaminated surfaces and then put their fingers in their mouth. For example, the viruses can land on the TV remote control. When you are flipping channels and eating popcorn, you may eat the virus.
It stands to reason that if virus particles can be aerosolized when a person vomits, the same phenomenon can occur when a person has explosive diarrhea. I have no scientific evidence to back me up, but I suspect that when you walk into a bathroom that smells horrid from a person having diarrhea, there may also be viruses in the air. Stinky public bathrooms are no longer just a funny joke.
Norovirus can be present in saliva, unfortunately.
Everyone else, including the CDC, will tell you that norovirus is only present in vomit and diarrhea. However, norovirus is probably present in saliva in some people. Here is a research article that checked saliva samples from a family of 6 who all had norovirus. They took saliva samples every morning for 18 days and checked them for norovirus using RT-PCR. You won't be able to read the entire article unless you buy it. I bought it. The results show that all 6 family members had norovirus present in their saliva for 9-13 days after the vomiting STOPPED from norovirus! 2 of the family members who never had vomiting (only diarrhea) still had norovirus present in their saliva for 10 and 13 days!!! That is really, really upsetting. I could only find one research article that investigated this. Hopefully, more research will be done so we can be certain of how scared we need to be. Rotavirus has also been shown to be present in nasal secretions 2,3,4. Therefore, people coughing and spitting when they talk can contribute to the spread of norovirus and rotavirus.
Contaminated Food and Water
Viral gastroenteritis is often spread through contaminated food and water. Third World countries with poor sanitation are ravaged by these illnesses. Here in the United States we generally have clean municipal water (I don’t want to think about the fact that our drinking water is not regularly tested for these viruses) but we still have an occasional problem with food6. Shellfish harvested from waters contaminated with sewage are frequently the cause of norovirus outbreaks. Fresh fruits and vegetables irrigated with water contaminated with sewage have caused outbreaks7. If a restaurant or cafeteria worker is contagious with viral gastroenteritis, they can easily contaminate your food. If several people get sick 2 days after a family reunion, it may not be that the potato salad was left in the sun too long. It may be that Aunt Frieda is getting over the stomach flu, and her potato salad was contaminated with her virus. When these viruses are transmitted through food it is called food borne illness. It is a type of food poisoning that is contagious.
--Annie Pryor, Ph.D.