The incidence of norovirus, a highly contagious stomach ailment causing vomiting and diarrhea, is surging in the United States, particularly in the Northeast. Despite the respiratory virus season likely being past its peak, the norovirus season for 2023-2024 is currently underway, with national circulation reaching the highest levels since the previous March, according to the latest data from the U.S. Centers for Disease Control and Prevention (CDC).

Norovirus, also dubbed the "stomach flu" or a cause of food poisoning, spreads readily, especially in enclosed environments. Since January 2024, there have been three confirmed norovirus outbreaks on cruise ships under U.S. jurisdiction, affecting hundreds of passengers, as reported by the CDC.

With the increasing number of cases and outbreaks, public health officials are urging Americans to take preventive measures. Despite its colloquial name, norovirus is unrelated to the flu, caused by influenza viruses. It is a primary cause of acute gastroenteritis, leading to inflammation of the stomach and intestines, resulting in severe bouts of vomiting, diarrhea, nausea, and stomach cramps.

Symptoms typically manifest 12 to 48 hours after exposure, and while they are sudden and unpleasant, most individuals recover without medical intervention. Dr. Tara Narula, a medical contributor to NBC News, emphasized the impact of norovirus, stating, "This is the dreaded virus that leaves us in the bathroom for about a day or two, we’ve all been there."

Norovirus is highly contagious, with anyone susceptible to infection. Annually in the U.S., it causes approximately 20 million cases of vomiting and diarrhea, 465,000 emergency room visits, 109,000 hospitalizations, and 900 deaths, according to the CDC. Although norovirus can spread throughout the year, winter months are typically associated with more frequent outbreaks. Presently, norovirus rates are on the rise nationwide, with the latest CDC data indicating a positive test rate of 15.4% as of March 2, up from around 9% in mid-January.

In recent months, there has been a consistent increase in the number of outbreaks. Between August 1, 2023, and February 12, 2024, the 15 states participating in the CDC's NoroSTAT surveillance program reported 759 norovirus outbreaks. In comparison, during the corresponding period in the previous seasonal year, there were 521 reported outbreaks.

A spokesperson for the CDC informed that the current level of norovirus outbreak activity in the United States falls within the expected range for this time of year and aligns with the reported range in previous years during the same time periods.

The CDC spokesperson added, "Typically, there is a surge in norovirus cases during winter, and we are actively monitoring the situation."

Where is norovirus spreading?

Nationwide, communities are grappling with the impact of norovirus outbreaks, with certain regions experiencing more significant challenges than others.

The Northeastern part of the country stands out with the highest positivity rate, surpassing last winter's peak levels. As of March 2, the latest CDC data reveals that the average positivity rate over three weeks in the Northeast region exceeded 16.5%. Cities like Philadelphia have witnessed notable spikes in norovirus outbreaks, leading public health officials to emphasize precautionary measures, as reported by NBC Philadelphia.

A CDC spokesperson noted, "Data from the northeastern region of the United States look similar to what we would expect for this time of year."

Following the Northeast, the Midwestern U.S. emerges as the next heavily impacted region, recording a three-week positivity rate of nearly 13.4%, according to CDC figures. The Western U.S. follows closely behind.

Dr. Joanna Turner Bisgrove, a family medicine physician and assistant professor at RUSH University Medical Center, highlights a significant spike in norovirus cases in California, as reported by

In the Southern U.S., norovirus cases are steadily on the rise. In Fairhope, Alabama, an elementary school temporarily closed for two days due to a suspected norovirus outbreak that affected an "alarming" number of students and staff members, according to NBC News affiliate NBC15 in Mobile, Alabama.

Why is norovirus surging?

Norovirus cases and outbreaks typically exhibit a seasonal pattern, predominantly occurring between November and April. Dr. Ericka Hayes, senior medical director of infection prevention at Children’s Hospital of Philadelphia, points out that Norovirus follows a seasonal trend, with the peak usually observed between January and early March, as conveyed to

The winter months, characterized by colder weather, lead to increased indoor gatherings, providing favorable conditions for the rapid transmission of infectious diseases like norovirus, explains Bisgrove.

The ongoing surge in norovirus is not unexpected, according to experts, but rather a seasonal upswing that occurs annually during winter in the United States. Bisgrove notes, "It’s following pretty classic trends."

Last winter marked a challenging norovirus season in the U.S., witnessing a rebound in virus activity to pre-pandemic levels following the relaxation of COVID-19 restrictions. Although cases peaked in early March 2023, norovirus activity remained elevated well into the spring.

In 2023, norovirus outbreaks also experienced a notable increase on cruise ships, reaching the highest levels seen in over a decade.

Dr. Hayes emphasizes that the current situation is comparable to previous years, with the number of outbreaks regionally and nationally falling within the normal range, if not slightly higher.

How does norovirus spread?

"Norovirus is an extraordinarily contagious virus, being one of the most contagious pathogens, whether viral or bacterial," emphasizes Hayes.

Infected individuals release billions of norovirus particles in their stool and vomit, with Hayes pointing out that only a few virus particles are sufficient to cause illness in another person.

The transmission of norovirus commonly occurs when individuals ingest these minuscule particles, as previously reported by This can happen through direct person-to-person contact, consumption of contaminated food or liquids, or touching contaminated surfaces and subsequently putting unwashed fingers in the mouth.

Bisgrove notes that norovirus can rapidly spread through environments such as schools, daycares, nursing homes, and other enclosed settings where people are in close proximity. The CDC identifies norovirus as the leading cause of foodborne illness outbreaks in the U.S.

Furthermore, even after symptoms subside and individuals start feeling better, a person who has been infected may continue to shed the virus for approximately two weeks, according to Bisgrove.

Norovirus symptoms

Experts outline the most prevalent symptoms of norovirus in both children and adults as follows:

  • Vomiting
  • Diarrhea
  • Nausea
  • Stomach cramps

Additional potential symptoms of norovirus, as outlined by the CDC, include a headache, body aches, and a low-grade fever.

The initial indicators of norovirus might involve a sudden loss of appetite, stomach pain, or a general feeling of being unwell, notes Bisgrove.

These initial signs are typically succeeded by intense vomiting and watery diarrhea, which may occur simultaneously. Hayes describes the onset as usually abrupt and substantial, with patients potentially experiencing dozens of stools per day.

Norovirus symptoms typically persist for 24 to 72 hours. Bisgrove mentions, "Due to all the vomiting and diarrhea, you may also feel weakness, fatigue, or lightheadedness."

Dehydration is a concern for individuals with norovirus due to the loss of fluids through vomiting and diarrhea. Symptoms of dehydration, as per the CDC, include reduced urination, dry mouth, or dizziness. In children, signs may include crying without tears, increased fussiness, or sudden lethargy and sleepiness, according to Hayes.

Notably, blood in vomit or stool is not a typical symptom of norovirus, emphasizes Bisgrove, and could indicate a more serious issue. "If you observe blood, seek medical attention and go to the emergency room," advises Bisgrove.

Norovirus treatment

There is no specific treatment or medication designed for norovirus, and the majority of individuals will naturally recover at home, according to the experts.

Resting and replenishing fluids and electrolytes lost through vomiting and diarrhea are crucial, advises Bisgrove. Suitable options include water, sports drinks, and oral rehydration fluids, with a caution to avoid beverages containing caffeine or alcohol until recovery.

"We also recommend bland, simple foods (such as rice, bananas, broths) that the body can handle and are more likely to stay down," adds Bisgrove.

If symptoms worsen, persist for an extended period, or if it becomes challenging to retain fluids or urinate, seeking medical care is recommended, states Bisgrove. In some cases, individuals may require additional support or intravenous (IV) fluids to prevent dehydration or its complications.

Certain populations are at a higher risk of complications, including children, the elderly, and individuals with chronic illnesses or weakened immune systems, notes Bisgrove. The CDC highlights that children under 5 years old and adults aged 85 and older are more likely to visit the emergency room in cases of norovirus.

Preventing norovirus

Norovirus is an exceptionally resilient virus. "It's challenging to disinfect, and it exhibits resistance to many standard cleaners," states Narula.

The experts emphasize that alcohol-based hand sanitizers are not very effective against norovirus. Therefore, thorough hand-washing is crucial. This entails washing hands with soap and water for a minimum of 20 seconds, as recommended by the CDC. It is especially important to wash hands after using the bathroom, changing diapers, and before eating.

If you are unwell with norovirus, the experts recommend taking the following measures to prevent spreading the virus to others:

  • Stay home until you feel better.
  • Avoid contact with others if possible while you are sick.
  • Wash hands thoroughly before touching any communal surfaces.
  • Clean and disinfect surfaces using bleach.
  • Wash laundry in hot water.
  • Refrain from preparing and handling food until at least 48 hours after symptoms have ceased.