What doctors wish patients knew about the contagious norovirus

It seems as though everyone has experienced a sudden turn of the stomach, causing a mad rush to the bathroom due to vomiting, diarrhea or both. And, unfortunately, remaining near the bathroom may be the only plan for the next day or two. The most likely culprit is norovirus, and it can happen to anyone at any time. Knowing what to do—and how to prevent norovirus infection—is key. 

Commonly called the “stomach bug” or “stomach flu,” norovirus is the leading cause of vomiting and diarrhea from acute gastroenteritis, which is inflammation of the stomach and intestines. In the U.S., norovirus causes 19–21 million cases of vomiting and diarrhea illnesses annually, according to data from the Centers for Disease Control and Prevention (CDC).

Norovirus also kills about 900 people—mostly adults 65 or older—and causes 109,000 hospitalizations, 465,000 emergency department visits and 2.7 million outpatient clinic visits each year, says the CDC.

The AMA’s What Doctors Wish Patients Knew™ series provides physicians with a platform to share what they want patients to understand about today’s health care headlines.

In this installment, two physicians took time to discuss what they wish patients knew about norovirus. These AMA members are:

• Joanna Turner Bisgrove, MD, a family physician and assistant professor of family medicine at Rush University Medical Center, and member of the AMA Council on Science and Public Health. She is also an AMA delegate for the American Academy of Family Physicians.
• Robyn F. Chatman, MD, MPH, a family physician in Cincinnati, and delegate in the AMA House of Delegates for the Ohio State Medical Association. She is also past chair of the AMA Council on Science and Public Health.

In the U.S., the three-week average for test positivity for norovirus is 15.4%. For the Northeast, the numbers of recent positive tests have reached over 16.5% compared with 12.6% in the South, 13.4% in the Midwest and 12.8% in the West, according to the CDC.

And while these numbers seem high, these levels are slightly below last season when about 15% of tests were positive for norovirus across the country.

“Norovirus is a human virus that is typically transmitted by the fecal-oral route,” Dr. Chatman said. “That just means that we’ve handled something that is contaminated and once it’s on our hands, we do all kinds of things with our hands.”

In fact, people with norovirus shed billions of virus particles both in their stool and in vomit. And the virus can linger on objects and surfaces for days or even weeks, spreading easily in crowded environments such as nursing homes, day care centers and cruise ships.

“This virus is very easily transmitted from one person to the next,” she said, noting that norovirus “is the most common cause of … gastroenteritis. And that’s just a big word that means an inflammation of the gastrointestinal tract.”

“That causes vomiting, nausea, stomach cramping and diarrhea,” Dr. Chatman said. “The good news is that it only lasts usually for 24 to 72 hours, but it is so easy to transmit from one person to the next that strict handwashing and use of household cleaners to sanitize hard surfaces is our best defense.”

Dr. Bisgrove recalled that she once acquired a norovirus infection by simply using the same bathroom that had been used earlier in the day by a visiting in-law who was recovering from a recent bout with the stomach bug.  That’s because “people who have norovirus can shed the virus for up to two weeks after their symptoms are gone.”

“I got norovirus and since I was pregnant, I was extremely dehydrated and had to go to the hospital,” she explained.

“The most common method of diagnosis is based on symptoms,” Dr. Chatman said. “It’s the physician evaluating the patient and listening to their symptoms and making a clinical diagnosis based on their symptoms.”

However, if the physician is concerned and wants to determine the etiology, there are stool PCR tests to help in diagnosis.

“It really can affect anybody. However, it’s the folks at the extreme ends of the age spectrum who are at greatest risk,” Dr. Chatman said. “Children between 6 months and 18 months are a high-risk group. And that’s daycare age, so they are not only at higher risk, but that’s the place where it’s spread so easily.”

“The opposite end of the spectrum are seniors, especially those who are living in a community setting like a nursing home,” she said. “They have more health issues and are more likely to be living in a community setting where if one person gets it, it can be easily transmitted from there.”

“We do commonly call norovirus the stomach flu, although it's not an influenza virus,” said Dr. Chatman. “It is a stomach bug, but it is a virus, so antibiotics have absolutely no effect on it.”

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“November to April is when norovirus is most common, but it can technically occur any time of year,” Dr. Bisgrove said. “It has everything to do with more people are inside and more people are sharing utensils, but it can be all year.”

“We hear about it on cruise ships because you’ve got these packed environments, but cruise ships only account for about 1% of outbreaks,” she said, noting it most commonly spreads in “health care facilities, restaurants, catered events, schools and child care centers.”

Additionally, “your sushi, dark and leafy greens, fresh fruits, raw shellfish—all can be a cause of norovirus,” Dr. Bisgrove said. “If you’re eating sushi, make sure you’re in a top-notch place where they keep everything clean.”

Norovirus can spread through food that is contaminated, which is why it is sometimes referred to as food poisoning—it is the leading cause of foodborne illness in the U.S. The source is often contaminated water. Oysters are a common culprit.

“Twenty million people a year get norovirus in the food industry—it’s the most common cause of foodborne illness,” Dr. Bisgrove said. And “the biggest reason is that food workers come to work sick or they get sick at work.

“There’s a vomiting episode or a diarrhea episode and it’s very hard to clean up,” she added, noting that most “of norovirus outbreaks for food is caused by workers, and the CDC talks about how observation of food-service workers have shown that they only practice proper hand washing about one in four times.”

To prevent foodborne norovirus, rinse fruits and vegetables with clean running water and cook shellfish thoroughly.

“Everybody goes into the bathroom, and they see the sign for the workers: Please wash your hands,” Dr. Bisgrove said. “That's mainly because of the norovirus. But you really have got to wash your hands.

“They talk about, especially with COVID-19, wash your hands while you're singing the happy birthday song. And that has been around because of norovirus,” she added.

“The biggest thing is hand washing, especially before and after you eat, and certainly after leaving the restroom,” Dr. Chatman said. “No matter where that restroom is, make sure you’re washing your hands.”

A person who is infected, according to the CDC, can transmit norovirus for up to two weeks after they're feeling better. That is why the best way to prevent norovirus is to sanitize frequently touched surfaces.

That means “disinfecting hard surfaces, doorknobs, telephones, cell phones, counters,” Dr. Chatman emphasized. “And for the little ones, it’s their toys and things that they’re going to be touching.”

But “getting norovirus off of surfaces is tricky because it is resistant to most disinfectants and hand sanitizers,” Dr. Bisgrove said. In fact, norovirus “can stay on food, countertops and serving utensils for up to two weeks, even at freezing temperatures and until heated to above 140º F.”

Another important prevention measure is to “stay home when sick. This is your standard public health prevention—stay home when sick,” Dr. Bisgrove said. “And if there’s a vomiting episode or something happens, just shut the place down and clean, clean, clean.”

“Everything is about prevention—the same way we approach COVID-19,” she said.

“If the symptoms last more than 72 hours, that’s the time when you want to go make an appointment to see your primary care physician,” Dr. Chatman said.

Before preparing and eating your food, “thoroughly wash and rinse some vegetables,” Dr. Bisgrove said, noting it is also important to cook oysters and other shellfish thoroughly to an internal temperature of at least 145º F.

“And if you are sick, you should not prepare or handle food,” she said.

“The key thing is hydration. The diarrhea and the vomiting can cause patients who are infected to lose body fluids,” said Dr. Chatman. “So, it's really of paramount importance to replace those fluids.

“Gatorade, Powerade—any of those beverages that are not carbonated, that don't have any citric acid in them, but do have electrolytes—are the best fluids for” mild dehydration, she added, noting “certainly no caffeine as well.”

“Norovirus can last for 24–48 hours. And if you can keep fluids down enough that you can urinate, you can most likely stay at home and let it run its course,” Dr. Bisgrove said. “We always talk about Pedialyte because you’re losing electrolytes as well as fluids. Pedialyte for kids is great and for adults too.”

When it comes to taking flu and cold medicine, “it’s really just going to make you more dehydrated,” Dr. Chatman said. “You should not use any of the over-the-counter cold preparations because it’s not related to influenza.

“Now, there are some cases where things like Kaopectate, Lomotil might be effective, but that's in adults only,” she added. “We want to be careful not to give children any of what we call antiemetics or anti-diarrheas without a physician's advice.”

“When people feel like eating, we’ll talk about what’s called the BRAT diet—bananas, rice, apple sauce and toast,” Dr. Bisgrove said. “These are all bland foods that help constipate you.”

“Bland foods that help constipate are extremely important and that’s why, for juice, I will often recommend apple juice because it can help return your stools to normal,” she said.

“The reason for this is that your body has completely wiped out all lactase [in your intestines] from the diarrhea, so there’s transient lactose intolerance,” Dr. Bisgrove explained.

“I get people with any kind of diarrhea illness, and they'll come in and they say they were feeling better and then they have diarrhea again,” she said. “Stop the dairy for at least 48 hours after symptoms are done and just let your body rebuild that lactase enzyme and then you’ll be OK.”