BANGOR, Maine — If you’ve been feeling under the weather lately, you’re not alone.

As is the case each year at this time, Maine has been hit by noroviruses, a group of viruses that cause acute gastroenteritis. The primary symptoms of noroviruses — also known as “winter vomiting disease,” are intense bouts of vomiting, diarrhea and cramping that typically last 24 to 48 hours.

“It’s all over — from Aroostook County to York, from Androscoggin to the midcoast,” state epidemiologist Dr. Stephen Sears said early Thursday evening in a telephone interview from his home, where he was hard at work despite a snowstorm that shut down state offices.

“We’re seeing outbreaks everywhere,” including schools, nursing homes, day care facilities and other institutions, he said. In January, about one-third of Wisdom Middle-High School’s staff and students were hit by noroviruses.

Sears said there is no way to know how many people have suffered from the highly contagious intestinal virus, which often is mistaken for the common flu. While clusters of norovirus cases must be reported to the state, individual cases need not be, he said.

So far this winter, however, the Maine Center for Disease Control and Prevention has seen at least 30 different outbreaks, Sears said.

And the norovirus season isn’t over yet. Sears said that more than 80 percent of norovirus outbreaks occur from November to April.

He said it is still too early to determine how this winter will stack up to last winter, when the Maine Health and Environmental Testing Laboratory saw 62 confirmed outbreaks and 22 suspected outbreaks.

Though norovirus is not a deadly disease, it is easily spread and immunity after having had it lasts only a few months, he said. “So someone could get it every six months,” he said.

Sears said Thursday that noroviruses are contagious and can spread easily through physical contact, the air and through stool and vomit.

To that end, he recommends that anyone who has symptoms should stay home to avoid spreading it to others. He also recommends that people wash their hands, especially before eating or preparing food and after using the toilet or changing diapers.

Because norovirus is so easily spread, Sears said it is not unusual to see places like nursing homes post signs asking visitors to stay away.

According to a Maine CDC fact sheet, people infected with norovirus are contagious from the moment they begin feeling ill until at least two days after recovery. Some people may be contagious for as long as two weeks after recovery.

According to Maine CDC, most people get better within a day or two and have no long-term health effects. Sometimes, however, people are unable to drink enough liquids to replace the liquids they lost because of vomiting and diarrhea.

That can lead to dehydration and may require medical attention. The dehydration problem is usually only seen among the very young, the elderly and persons with weakened immune systems.

Currently, there is no medication that works against norovirus and there is no vaccine to prevent infection, the Maine CDC says. It can’t be treated with antibiotics because antibiotics work to fight bacteria, not viruses.