CDC Data: Norovirus Cases on the Rise in the US, Namely the Northeast

Transmission electron micrograph shows norovirus particles in an undated file photo. (Charles D. Humphrey/US Centers for Disease Control and Prevention)

Norovirus has been on the rise across the northeastern United States over the past month or so, according to recent data provided by the U.S. Centers for Disease Control and Prevention (CDC).

More than 13 percent of tests for the virus, which is associated with vomiting and diarrhea, came back positive as of mid-February, the most recent CDC data revealed. That’s the highest level in any region of the country.

Nationwide, 12 percent of tests for norovirus have come back positive during the same period, the data show. In mid-January, about 10 percent of tests came back positive.

That’s lower than the 15 percent positivity rate from a year ago, and it’s also lower than the 14 percent positivity rate in 2022, according to the data.

“Participating U.S. laboratories report the total number of norovirus tests performed that week, and the number of those tests that were positive to CDC weekly,” the agency wrote on its website. “Because reporting delays may be expected for some laboratories, data shown for the more recent weeks may be less complete than others.”

The CDC noted that norovirus is often highest in the late fall, winter, and early spring. It is associated with restaurants, schools, hospitals, camps, cruise ships, and other venues, with health officials saying it is the largest source of foodborne illness in the United States. The virus is often called “food poisoning” or the “stomach flu.”

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For example, a norovirus outbreak connected to a North Carolina sushi restaurant left at least 241 people sick, officials said in December 2023. Earlier that year, a school in California reported 136 cases of the virus, prompting officials to shut it down.

Sometimes dubbed the “cruise ship virus,” norovirus is highly contagious, with about 90 percent of “outbreaks of diarrheal disease on cruise ships” being caused by the virus, according to the CDC.

“These outbreaks often get media attention, which is why some people call norovirus the ‘cruise ship virus,’” the CDC’s website reads. “However, norovirus outbreaks on cruise ships account for only a small percentage (1 percent) of all reported norovirus outbreaks. Norovirus can be especially challenging to control on cruise ships because of the close living quarters, shared dining areas, and rapid turnover of passengers.”

It noted later that “repeated outbreaks on consecutive cruises may also result from infected crew or environmental contamination. This is because norovirus can persist on surfaces for days or weeks and is resistant to many common disinfectants.”

In January, about 100 people were sickened on a Celebrity cruise ship, with the main symptoms being diarrhea and vomiting, CDC officials said. About a month later, the CDC reported that an “unknown” illness caused about 150 people to become ill on another cruise, with vomiting and diarrhea symptoms that appear to be consistent with norovirus. However, the agency still hasn’t identified the cause.

The virus can infect people of all ages and cause gastroenteritis, or inflammation of the stomach and intestines, according to officials. It can spread via contaminated water, food, surfaces, or direct contact with an infected individual, while infection usually starts within 24 to 48 hours of exposure and lasts up to three days.

In a normal year, according to the CDC, norovirus causes 19 million to 21 million cases of vomiting and diarrhea, 109,000 hospitalizations, and 900 deaths across the United States. The virus also is associated with about 495,000 emergency room visits, mostly in younger children, according to the CDC. Most outbreaks occur between November and April. If there is a new strain of the virus, it says, there can be 50 percent more norovirus illness.

There is no cure for norovirus, but officials recommend drinking a lot of fluids to prevent from becoming dehydrated. Generally, the virus lasts only a few days.