Rotavirus, Norovirus or Stomach Flu: What's the Difference?

As common infectious diseases go, norovirus is fast and furious. "It usually comes on quickly [and] suddenly with vomiting and diarrhea," says Dr. Jason Newland, a pediatric infectious disease doctor at St. Louis Children's Hospital and a professor of pediatrics at Washington University School of Medicine. "It lasts about 24 to 60 hours for normal healthy people, and it doesn't take a lot of this virus to cause you to get sick."

In fact, norovirus is the leading cause of diarrheal illness in the U.S. among adults. According to the Centers for Disease Control, 21 million cases are reported each year. When the symptoms of norovirus or a similar viral infection called rotavirus that's more common in children hit, those affected often refer to their affliction as the " stomach flu." Yet the term is a misnomer, as none of these are caused by a flu virus.

What Is a Stomach Flu?

Instead, stomach flu -- more correctly known as gastroenteritis -- generally refers to an irritation of the stomach or gastrointestinal tract, which can cause diarrhea, vomiting and stomach pain.

"Many, many viruses and many bacteria can result in symptoms that someone would describe as a stomach flu -- which can be misleading," says Dr. Lukasz Weiner, a pediatric infectious disease doctor at University of Iowa Hospitals and Clinics. He prefers the term gastroenteritis. "I think it's a more accurate term medically. But I know people use the term stomach flu to describe something similar."

Norovirus and rotavirus are, in the medical parlance, both spread by what's called fecal-oral transmission. That is to say there's no getting around the disgusting way these highly contagious diarrheal illnesses are rapidly passed from one victim to the next.

"The transmission is out the rectum of one person and in the mouth of somebody else," explains Dr. Robin Colgrove, an infectious disease doctor at Mount Auburn Hospital in Cambridge, Massachusetts, and an assistant professor of medicine at Harvard Medical School. "So they're transmitted by stool." Even microscopic bits of stool from watery diarrhea can carry the virus.

It's also a hearty virus, Newland adds. They will linger on counter surfaces. Unsanitary conditions further fuel the spread of these infectious diseases. In developing parts of the world, they are typically spread via the water supply. In contrast, in the U.S. and other developed countries, they're commonly spread when people are in close quarters, like daycare centers, hospitals and cruise ships.

They can also be spread through food preparation. In fact, norovirus is a leading cause of foodborne illness. That's led to restaurants grappling with headline-grabbing outbreaks of the hard-to-shake disease.

The Difference Between Norovirus and Rotavirus

Medical experts say it's difficult, if not impossible, to be able to distinguish between norovirus and rotavirus based on symptoms alone. For each those include:

Norovirus:

-- Nausea.

-- Vomiting.

-- Watery diarrhea.

-- Stomach pain.

-- Fever.

-- Body aches.

Rotavirus:

-- Vomiting.

-- Watery diarrhea.

-- Fever.

-- Abdominal pain.

-- Dehydration.

[SEE: Can You Trust Your 'Yuck' Reflex?]

The primary differences between norovirus and rotavirus are based on who gets it, how long the infection typically lasts and the possible complications. The norovirus typically lasts no more than about two and a half days, while rotavirus generally lasts three to eight days. Because rotavirus typically affects babies and young children, that loss of fluid is more significant than it would be for adults. Severe dehydration, especially for infants and young children, can be life threatening.

While kids can get norovirus too, this virus is seen more in adults. "Norovirus is the most common cause of acute diarrhea in adults in developed countries," Colgrove says. This is different from diarrhea from chronic conditions like inflammatory bowel disease or that's caused by a bug someone picked up from traveling abroad.

Rotavirus, on the other hand, was the most common cause of acute diarrheal illness in children in the world before vaccination against the disease was available. "Before we had a vaccine for it, there were millions of hospitalizations and hundreds of thousands of deaths per year among young children," Colgrove says. Now highly effective infant vaccines provide protection against it. So while some kids do still get rotavirus in the U.S., illnesses and hospitalizations have plummeted as a result of routine vaccination.

Although norovirus generally passes more quickly, the infectious disease can linger in more vulnerable populations, like older adults who have other health issues. "The main complication of either of these infections is severe dehydration -- which is the main reason that young children or the elderly, for example, require hospitalization," Weiner says.

Adults who've had rotavirus as children, typically develop a lifelong immunity to it. But with norovirus, a person can get infected repeatedly. It's harder for the body to build up a defense against it because the virus is much more prone to change or mutate. (There's no vaccine for norovirus.)

[See: 9 Ways to Boost Your Immune System.]

Treatment

Experts say there's little one can do but endure the symptoms of the diseases until they pass. Clinicians say no proven cures or effective treatments exist to reliably reduce the duration of either disease or significantly ease symptoms. "There are no treatments for either of these," Colgrove says. Anti-diarrhea medications are generally not helpful.

That said, experts emphasize the importance of hydration, including consuming electrolytes, while sick with norovirus or rotavirus. Rehydration drinks like Pedialyte may help to prevent the more serious complication of dehydration.

Regularly hydrating can prevent a dangerous loss of body fluids. "That's the key to keeping people out of the hospital," Newland says. "But sometimes (with) these little babies, it's just too hard because they have so much vomiting and diarrhea." That makes vaccination against rotavirus all the more critical.

Controlling Disease Spread

The fact that there are no proven effective treatments against norovirus and rotavirus is all the more reason, experts say, that otherwise healthy people should do their part to reduce the spread of these highly infectious diseases.

That includes having babies vaccinated against rotavirus. Depending on the vaccine, that involves shots when a baby is 2, 4 and 6 months of age" or just 2 and 4 months of age, Newland notes.

Of course, the most important thing anyone can do to protect against the spread of norovirus -- and rotavirus, apart from vaccination for that disease -- is hand-washing, experts say. The best method for hand-washing is actually simply using soap and water.

"The alcohol gels aren't as effective," Newland says. You won't likely inactivate these sturdy viruses. And you don't want to use gels that remain on your hands. Instead, Colgrove notes, you want to wash the viruses down the drain.

When washing your hands, be sure to scrub thoroughly for at least 20 seconds, the CDC suggests.

Additionally, clean surfaces, make sure you always wash food and don't prepare food at all when you're sick with a diarrheal illness.

While you're at it, stay home until the illness passes. "I think of this as a public service," Colgrove emphasizes. "An otherwise healthy person is unlikely to die from one of these infections, but they can kill somebody else if they give it to a frail person."

[SEE: Signs of a Cold You Shouldn't Ignore]

Be Alert to Serious Dangers

Because there are various illnesses that can cause gastrointestinal distress, it's important not to assume that what you have is, say, norovirus. And be alert to escalating symptoms that may signal you need to be seen right away by a health care provider.

Adults and kids shouldn't have a high fever with rotavirus or norovirus.

Viral gastroenteritis often causes low-grade fevers of typically less than 101.5 F in adults, Colgrove says. "High fevers greater than 102.5 F, particularly with shaking chills, is more suggestive of bacterial infections such as salmonellosis, which may require antibiotics."

Colgrove adds that with kids, its more complicated. "They can run quite high fevers even with otherwise mild infections," though usually not with shaking chills," he notes. "Parents of children with fever greater than 102 F should call their pediatrician and describe the symptoms, so they can get advice on whether to bring the child in to be evaluated."

Symptoms in babies tend to be subtler, so it's important for parents to monitor infants and young children even more closely. Contact your pediatrician right away if you have a concern about symptoms including fever.

Colgrove says high fever is one of several "alarm symptoms," a medical term referring to things that could indicate a potentially serious problem. Here are other alarm symptoms to look out for:

-- Not being able to take in as much fluids as you're losing.

-- Severe abdominal pain.

-- Blood in your vomit or diarrhea.

For these or any other concerning symptoms, seek immediate medical attention.

For anyone who has norovirus or rotavirus, experts reiterate the importance of regular hand-washing and not making a hasty return to work or life outside your home. Wait until you're healthy again, so you don't give one of these highly infectious diseases to someone else.