Since September, more than 140 outbreaks in the U.S. have been caused by the new Sydney strain of norovirus. It may not be unusually dangerous; some scientists don’t think it is. But it is different, and many people might not be able to fight off its gut-wrenching effects.

The new strain is making people sick in Japan, Western Europe, and other parts of the world. It was first identified last year in Australia and called the Sydney strain.

A report by the U.S. Centers for Disease Control and Prevention states the Sydney strain is now accounting for about 60 percent of norovirus outbreaks.

Sometimes mistakenly called stomach flu, the virus causes bouts of vomiting and diarrhea for a few days.

Every two or three years, a new strain evolves — the last was in 2009. The Sydney strain’s appearance has coincided with a spike in influenza, perhaps contributing to the perception that this is a particularly bad flu season in the U.S.

Norovirus is also the most common cause of food poisoning in the U.S.

Each year, noroviruses cause an estimated 21 million illnesses and 800 deaths, the CDC says.

Seven outbreaks have been confirmed across North Carolina so far in 2013. Years with new strains tend to have the highest numbers of cases because virtually no one has immunity, said Ralph Baric, a professor of epidemiology at the Gillings School of Global Public Health at UNC-Chapel Hill.

Noroviruses are more contagious than most viruses. People shed millions of the virus particles in their stool and vomit said Dr. Zack Moore, a medical epidemiologist for the state health department, but it only takes between 10 and 100 particles to infect someone.

“It’s such a common infection because it’s very hardy. It can live on surfaces in the environment if it gets onto them, and the usual types of disinfectants aren’t effective against it,” Moore said. “If there are areas that have been contaminated, you have to use a dilute bleach solution to kill the norovirus.”

CDC says, “proper hand hygiene, environmental disinfection, and isolation of ill persons remain the mainstays of norovirus prevention and control.”

For those infected, there’s really no medicine. They just have to ride it out for the day or two of severe symptoms, and guard against dehydration, experts said.

The illness got the attention of comedian Stephen Colbert, who this week tweeted: “Remember, if you’re in public and have the winter vomiting bug, be polite and vomit into your elbow.”