How Do You Get the Stomach Flu?
The miserable diarrhea, nausea, and vomiting known as the stomach flu isn’t actually from the flu. “Flu,” of course, is short for influenza, the viral respiratory illness.
While most cases of the so-called stomach flu are also caused by viruses, they’re from a totally different set of germs. The formal name for this intestinal inflammation–which usually comes on quickly and, thankfully, also leaves quickly–is “viral gastroenteritis.” (Bacteria and parasites cause some of these illnesses as well, but not as often as their viral cousins.)
“When people have acute gastrointestinal events [when] they feel stomachache, nausea, vomiting, and diarrhea, it’s usually one of these viruses,” says Deborah A. Fisher, MD, associate professor of medicine in the division of gastroenterology at Duke Health in Durham, North Carolina.
The most common viral culprit for the stomach flu? Norovirus, famous for causing outbreaks on cruise ships and in other close quarters like schools and nursing homes. “Noroviruses are hard to clean and easy to transmit,” says Dr. Fisher.
In the U.S. and other parts of North America, norovirus is most active between October and April. This coincides roughly with actual flu season, which may account for some of the confusion.
Other common causes are rotavirus, adenovirus (related to the same virus that causes the common cold, but typically different strains), astrovirus, and sapovirus.
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How does the stomach flu spread?
While you can get many of the same symptoms from eating contaminated food (aka food poisoning), most cases of the stomach flu are passed from person to person. Food poisoning is not spread person to person.
The viruses that cause this type of illness “are among the most contagious viruses that we have on the planet,” says Buddy Creech, MD, MPH, associate professor of pediatric infectious diseases and director of the Vanderbilt Vaccine Research Program at Vanderbilt University School of Medicine and Medical Center in Nashville. “The reason they’re so contagious is that some of them are spread through contact.”
Contact could mean breathing in airborne germs after someone vomits or coughs. Or it could mean shaking hands with someone who is sick, eating food prepared or served by someone who is sick, or touching a surface or dirty utensils contaminated with viral particles from vomit or even stool. Children are known for putting their fingers and all kinds of other objects into their mouths, but even grabbing your trusty iPhone and then touching your face could provide a convenient entry point for the germs.
“We can clean our hands, but if we put our phone down on every surface, our clean hands are no longer clean,” Dr. Fisher says. This can be an especially risky practice in public spaces like airports.
An estimated 9% to 25% of mobile devices are contaminated with a disease-causing organism, adds Dr. Fisher. Wipe your devices down at least daily, and keep washing your hands on the regular.
RELATED: 20 Reasons Why Your Stomach Hurts
When is the stomach flu contagious?
Unfortunately, the different viruses responsible for stomach flu can be contagious before you even know you–or someone else–is sick.
Norovirus symptoms usually start 12 to 48 hours after coming into contact with the virus and last one to three days. But the virus can be detectable in your poop not only before you have symptoms but up to two weeks after you recover. “You can get better after 24 hours but still have the virus for several days,” says Dr. Creech.
Norovirus can also survive for weeks on hard surfaces like countertops.
Rotaviruses cause stomach flu symptoms within about two days, adenoviruses within about three to 10 days, and astroviruses within five days. All of these may last longer than illnesses attributed to norovirus.
How to prevent the stomach flu
Once you have the stomach flu, there’s little you can do but suffer through it, making sure you drink lots of fluids so you don’t get dehydrated (one of the major potential complications of viral gastroenteritis).
“It’s contagious, happens quickly, and there’s no good treatment,” says Dr. Creech. “That’s really our challenge. Our job is to keep people hydrated and just carry them through.”
There is a vaccine that can be given to babies to protect against rotavirus. But for everyone else, it’s all about washing your hands (a lot), whether or not you know there are sick people around. Soap and warm water are best, but alcohol-based sanitizers (make sure they’re at least 60% alcohol) will do if you don’t have access to a sink.
“Hygiene is always at the top of the list–washing your hands after using the restroom, before you prepare food,” says Dr. Creech. Steer clear of anyone who is sick, and stay home if you yourself have the stomach flu. Disinfect countertops and other hard surfaces and wash linens well if you or someone else at home gets sick.
Pregnant women, older adults, small children, and anyone with a compromised immune system are vulnerable to more severe bouts of stomach flu. See a doctor if viral gastroenteritis lasts more than three days or if you can’t keep liquids down for 24 hours.
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