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What to Know About Norovirus, the Highly Contagious “Stomach Bug” Sweeping Across the US

Emily Turner

As the White House begins to wind down the COVID national and public health emergencies, another highly contagious virus may be making its way through the country. Norovirus cases are rising across the United States and England, with an average of 15 percent of norovirus tests administered in the US coming back positive over three weeks, according to data from the Centers for Disease Control and Prevention (CDC). That’s the highest rate since March 2022.

So if you’ve had more than one friend cancel plans due to a nasty “stomach flu” or “stomach bug,” they might actually have norovirus — which means you could be at risk, too. Norovirus doesn’t discriminate with age. In fact, several schools across the country have reported outbreaks, while others have had to close down due to the virus.

“Norovirus is extremely contagious,” says immunologist and microbiologist Andrea C. Love, PhD, cohost of “The Unbiased Science Podcast” and advisory board member for POPSUGAR’s Condition Center. The virus is so easily transmissible that “fewer than 20 viral particles can infect someone,” Dr. Love says.

While it is not actually a stomach flu and has no relation to influenza viruses, its symptoms are similar. Norovirus is “characterized by violent vomiting,” explains Amesh Adalja, MD, senior scholar at the Johns Hopkins University Center for Health Security. “Diarrhea, fever, and muscle aches and pain can also occur, but the vomiting is the most impactful symptom.”

While there isn’t a vaccine or specific treatment for norovirus, symptoms can be managed at home. And of course, preventative strategies and knowing the signs and symptoms can help you avoid contracting the virus in the first place. Read ahead to learn more about the highly contagious norovirus.

What Is Norovirus?

Norovirus is a very contagious virus and “the most common cause of acute gastroenteritis (inflammation of the GI tract),” Dr. Love says. People of all ages can become infected with norovirus, resulting in severe vomiting and diarrhea, according to the CDC.

One thing to note about norovirus: unfortunately, you can get the illness many times throughout your life, as there are many different kinds of noroviruses. “Infection with one type of norovirus may not protect you against other types. It is possible to develop immunity to (protection against) specific types. But, it is not known exactly how long immunity lasts,” the CDC states.

What Are the Most Common Symptoms of Norovirus?

A person will typically develop norovirus symptoms within 12 to 48 hours of being exposed, according to the CDC. The most common symptoms include:

  • vomiting
  • diarrhea
  • nausea
  • stomach pain

“Norovirus is a virus that causes gastrointestinal illness,” particularly gastroenteritis, or inflammation of the stomach and intestines, Dr. Adalja says. It’s not uncommon for someone with norovirus to throw up or have diarrhea several times a day. This can also lead to dehydration. Other norovirus symptoms to watch out for include fever, headache, and body aches.

How Is Norovirus Spread?

“Norovirus is spread through close contact with someone who has norovirus, through surfaces contaminated with the viruses, or in the air after someone has vomited,” Dr. Adalja says. Fecal-oral contact and food and water sources can also be responsible for the spread of the virus, Dr. Love adds.

Outbreaks can be very common in high-density areas where people are in close quarters, like day cares and cruise ships, she says. Not to mention, “norovirus is the leading cause of illness and outbreaks from contaminated food in the United States,” per the CDC. So many of the outbreaks happen in food-service settings.

And even after you recover from the virus, you may still shed it in your stool for weeks to come. “So if proper hygiene is not implemented, that can propagate continued outbreaks,” Dr. Love says.

How Can You Tell Norovirus Apart From Food Poisoning or a Stomach Bug?

It can be tricky, especially when people use catchall terms, like food poisoning or stomach bug, to generally describe how common norovirus symptoms present themselves. “It is very difficult to differentiate different gastrointestinal illnesses from each other, but the dramatic and sudden vomiting is something very specific to norovirus,” Dr. Adalja says. Also, other viruses tend to differ in symptoms and duration of illness.

“For example, norovirus symptoms typically are very short-lived, whereas rotavirus (another virus that causes vomiting and diarrhea) symptoms can persist for up to eight days,” Dr. Love says. Another differentiation: stomach viruses typically do not cause bloody stool, whereas bacterial infections due to food poisoning can in some instances, she adds.

Also, norovirus has an incubation period of 12 to 24 hours, whereas some cases of food poisoning can present symptoms within hours of consuming contaminated food products, Dr. Love says.

What’s Causing the Current Norovirus Outbreak?

According to Dr. Adalja, norovirus typically spreads in the winter months. But viral outbreaks like this one have become a more prominent part of media coverage since COVID. “The majority of outbreaks typically occur from November to April in countries above the equator, and from May to September in countries below the equator,” per the CDC.

Is Norovirus Deadly?

“For most people, norovirus infection usually clears up within a few days and isn’t life-threatening,” according to Mayo Clinic. That being said, the illness can be very severe for some, especially young children, older adults, those with compromised immune systems, and those who are pregnant. And in some cases, norovirus can result in dehydration, hospitalization, and death.

But again, the majority of people will recover within a few days.

What Is the Treatment For Norovirus?

Unfortunately, there isn’t a specific treatment for norovirus. There is no vaccine, either, Dr. Love says. Treatment typically involves managing symptoms at home and focusing on fluid and electrolyte replacement to avoid dehydration.

What Are the Best Preventative Strategies to Avoid Norovirus?

Good handwashing is key in protecting yourself against the spread, Dr. Adalja says. Make sure to wash your hands with soap and water, rather than relying on alcohol-based hand sanitizer as a cleansing method. Norovirus is what’s called a “non-enveloped virus, which means that it doesn’t have a lipid covering that some other viruses have,” Dr. Love says. Translation: hand sanitizer isn’t an effective way to combat the virus.

Besides that, you can aim to avoid the illness by steering clear of people with GI symptoms, cleaning commonly touched surfaces, properly washing clothing and bedding of individuals who’ve been recently sick, and practicing good food and water hygiene.

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