Dreaded noroviruses are once again spreading across US. What to know about stomach bug

As the so-called “stomach flu” season continues, new outbreaks are being reported on cruise ships and elsewhere in the United States. But what are noroviruses?

Each year, the United States experiences about 2,500 norovirus outbreaks, the U.S. Centers for Disease Control and Prevention said. They are most common from November to April.

Noroviruses kill an average of 900 people a year in the United States, mostly those 65 and older, the agency said. More than 100,000 people are hospitalized each year on average, and the virus results in 465,000 emergency room visits annually.

Although the resulting illness is sometimes called “stomach flu,” noroviruses have no connection to influenza.

More than 300 people fell ill, most likely from noroviruses, on a Princess Cruise ship that returned to port in Galveston, Texas, in February, McClatchy News reported.

In December, the Food and Drug Administration warned of a norovirus outbreak linked to raw oysters shipped from Texas. The CDC reported nearly 300 norovirus cases resulted from the outbreak.

Here’s what to know about the stomach flu:

What are noroviruses?

Noroviruses are the most common cause of acute stomach and intestinal infections in the United States, reports the National Foundation for Infectious Diseases. It’s also sometimes called stomach flu, viral gastroenteritis or the winter vomiting bug. The U.S. reports 19 million to 21 million cases a year. Humans are the only known hosts of the virus.

The virus was formerly known as the Norwalk virus because the first known outbreak took place at an elementary school in Norwalk, Ohio, according to norovirus.com. Scientists identified the virus in 1972 from stool samples stored after the outbreak. It was officially renamed norovirus by the International Committee on Taxonomy of Viruses.

How contagious are noroviruses?

Extremely. The CDC cautions that noroviruses can be transmitted by infected people, contaminated food or water, or just by touching contaminated surfaces. People sick with a norovirus are most contagious during the illness and for a few days afterward, and the virus can remain in stool for up to two weeks after the illness. The virus can survive temperature extremes, too.

Also, catching a norovirus doesn’t help you fight it off if you’re exposed to it later, in part because there are many different types of noroviruses — catching one doesn’t protect you from others.

Where do noroviruses spread?

Cruise ships, nursing homes, day care centers and schools are common breeding grounds for norovirus – anywhere large numbers of people are packed in close quarters, basically, the CDC reports. Outbreaks on cruise ships frequently make the news, and there are countless travel websites dedicated to tracking cruise lines with the worst track records for the illness.

What are the symptoms of a norovirus?

Diarrhea, cramps and vomiting usually start within 12 to 48 hours of exposure to the virus, according to the Mayo Clinic. Norovirus symptoms normally last one to three days, and most people recover without treatment. But infants, older adults and people with chronic illnesses may require medical attention for dehydration.

Since it’s a virus and not a bacteria, antibiotics aren’t any help, and there are no antiviral drugs for noroviruses.

The Mayo Clinic advises that people with norovirus take special care to replace fluids lost by vomiting or diarrhea to prevent dehydration. Drinks like Pedialyte are good for young children, while sports drinks and broths are suggested for adults. Sugary drinks, like sodas and fruit juices, can make diarrhea worse, while alcohol or caffeinated drinks can speed dehydration.

How long do norovirus cases last?

Most people recover in one or two days, but some cases can last up to a week, the Minnesota Department of Health said.

Most patients have no long-term effects but “dehydration can be a concern in the very young, the elderly, or people with weakened immune systems,” the agency said.

How can you avoid noroviruses?

Good hygiene is key to avoiding noroviruses, WebMD.com suggests. Wash your hands frequently with soap and water, particularly after using the bathroom and before preparing food. Alcohol-based cleaners, such as hand sanitizers, are not as effective. The site also advises carefully throwing away contaminated items, such as dirty diapers.

Wash raw fruits and vegetables, and cook oysters and other shellfish. Clean and disinfect surfaces with a mixture of detergent and chlorine bleach after someone’s sick, WebMD says. And if you catch a norovirus, don’t prepare food for at least two to three days after you feel better.

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