(CNN) -- The queen of England has something that most of us get at one point or another -- but usually gastroenteritis doesn't lead to a hospital stay.
Experts say, however, that anytime an older patient gets it, the complications can be more serious.
Dr. Won Kyoo Cho, the director of gastroenterology at MedStar Washington Hospital Center, says doctors are more likely to admit someone to the hospital when they are concerned about the patient not being able to keep anything in his or her stomach.
"When they get dehydrated, it usually it gets worse. We need to get them IV fluids" to replace potassium, magnesium and phosphorous, he says.
Dr. Corey Siegel, a gastroenterologist and assistant professor at Dartmouth, says dehydration can lead to kidney problems.
And the elderly are at especially high risk of getting dehydrated when they have gastroenteritis, he says.
Once treated, most symptoms disappear in a few days, Cho says.
Here are five things you should know about gastroenteritis:
1. It is often called the stomach flu, but it's not.
It often can be caused by a virus, but it's not an influenza virus. It can also be caused by bacteria or parasites, but that is rarer. The National Institutes of Health says viral gastroenteritis is the second most common illness in the United States. People exhibit symptoms of watery diarrhea, abdominal cramps, nausea or vomiting, and sometimes a fever.
2. It is rarely deadly.
But infants, older adults or people with compromised immune systems can have serious complications. That's because they are at risk for dehydration from loss of fluids, according to the Centers for Disease Control and Prevention. The Cleveland Clinic says about 27 people die each day in the United States from severe gastroenteritis. But most people recover without needing hospitalization, the NIH says. Cho says more than 3 billion people around the world get the disease each year.
3. It can be foodborne or waterborne, or you can get it from another person.
Gastroenteritis is contagious and can be spread through contact between someone who is infected and another person. It can also be spread by food (especially seafood) or drink that is contaminated, but that is less common. Prevention is key, the Mayo Clinic says, advising people to wash their hands frequently and avoid food or water or utensils that they think might be contaminated. Cho says when doctors diagnose the disease, they look for two things: symptoms and circumstances. The latter can help narrow down what type of gastroenteritis a person has.
4. It cannot be treated with antibiotics -- if it is viral.
The Cleveland Clinic also says doctors usually do not recommend antidiarrheal medications because they can prolong the infection. The best course of action is to replenish with fluids or foods that contain the most electrolytes or complex carbohydrates, the experts say. The CDC recommends keeping oral rehydration solution on hand and giving it to someone who has had diarrhea. Cho says doctors usually hold off for a few days before using antibiotics. "It can be a little bit tricky," he says, adding doctors usually take a stool sample to see if the cause is bacterial.
5. It can last up to 10 days.
It depends on the type of virus the patient has, the CDC says.
CNN's William Hudson and Elizabeth Cohen contributed to this report.