US health officials are on high alert due to a rising number of cases of a potentially deadly stomach virus.
Norovirus, also called the stomach virus or stomach flu, causes severe diarrhea and vomiting, which can lead to life-threatening dehydration, and is spreading rapidly across the country.
Norovirus infects about 21 million Americans annually, sending about 2 million of them to their doctor’s office or urgent care. Approximately 465,000 people with the virus go to the emergency department each year.
State health departments reported 91 norovirus outbreaks (considered a cluster of two or more cases stemming from a common source) during the week of Dec. 5, up from 69 the week before. For comparison, only two outbreaks occurred during the same week in 2021.
The virus spreads when someone is exposed to germs from the vomit or feces of a sick person. Someone can also get sick by eating contaminated food, sharing food or utensils with a person who carries the virus, and touching surfaces that a sick person has previously touched.
Doctors say illnesses can be avoided by thoroughly cooking seafood to at least 145 degrees, washing your hands with soap and water for at least 20 seconds, washing produce before eating it, sanitizing countertops, and avoiding people who have been infected.
Outbreaks are most common in congregate living facilities such as nursing homes and prisons, as well as on cruise ships and schools. Earlier this month, more than 300 passengers on three different cruise ships contracted norovirus.
Current data is not complete and the number of cases is likely higher than reported. The CDC does not report individual cases because the infection usually resolves on its own within a few days and is not diagnosed by a doctor or reported.
Just over a dozen states participate in the CDC’s national disease surveillance system.
Norovirus causes severe diarrhea and vomiting, which can lead to life-threatening dehydration.
According to the CDC: “This year, the number of reported norovirus outbreaks has exceeded the numbers we have seen recently and in the years before the pandemic.”
Norovirus cases tend to peak in the winter and early spring, when people are more likely to be indoors and around others infected with the virus.
Norovirus symptoms (nausea, vomiting, and diarrhea) appear quickly, within 12 to 48 hours after exposure.
Most people recover within a few days.
But the virus kills about 900 people a year, mostly adults 65 and older.
The infection can lead to serious complications, especially in people whose immune systems are already weak.
Dehydration is a major concern. When the body rapidly loses fluids and electrolytes through repeated vomiting and bouts of diarrhea, a person can experience dangerously low blood pressure, reduced blood flow to their organs, and an electrolyte imbalance that can damage the heart and muscles.
Electrolyte imbalances can also cause seizures and sometimes unconsciousness.
Norovirus is commonly transmitted from undercooked seafood that has been contaminated with the virus in water. Oysters are a common source.
They suck in large volumes of water to extract food particles. If that water is contaminated with norovirus, those oysters can consume virus particles that accumulate in their tissues and infect people who eat them.
Oysters are filter feeders, meaning they draw in large amounts of water from which they extract nutrients. If that water is contaminated with norovirus, they collect particles that accumulate in their tissues.
Norovirus infections are common on cruise ships due to the close quarters and shared facilities, such as pools and hot tubs, which can become infection hotspots.
Earlier this month, the FDA announced a widespread recall of oysters and clams harvested in Washington over possible norovirus contamination.
The recall did not mention any seafood-related illnesses, but recommended restaurants stop serving them and throw them away immediately.
A few days later, the recall was expanded to cover shellfish harvested in Canada. In total, potentially contaminated seafood was shipped to Arizona, California, Florida, Massachusetts, Michigan and New York.
People should avoid eating raw oysters, as cooking them is essential to kill the virus, which includes boiling them for at least three minutes, steaming them for at least four minutes, and frying, baking, or roasting them until the internal temperature reaches 145 degrees.
Virus particles can also end up on countertops and other kitchen work surfaces, such as cutting boards. Sanitizing them with disinfectant is key.
The particles can remain there for days or even weeks at a time.
Soap and water kill the virus better than hand sanitizers due to the unique structure of viral particles. Alcohol cannot penetrate the particles; hard outer shell.
And it only takes a few of those particles to make a person sick.
The virus is highly transmissible and a person can remain contagious for up to two weeks after symptoms disappear.
To reduce the chance of spreading the virus, the CDC recommends washing all bedding for as long as possible and drying it at the highest temperature. The infected person should also avoid the kitchen.
There is no antiviral treatment for norovirus and doctors recommend replacing fluids with sugar-free, electrolyte-rich drinks.
As for food, the milder the better, including clear broth, apple sauce, crackers, rice, and toast. Dairy products should be avoided, as well as fatty foods, spicy foods and alcohol.