The so-called stomach bug usually sneaks up on unsuspecting and seemingly healthy people exactly the way it invaded Julia Adams earlier this month. One Saturday, with her world just right, she painted the trim on her Franklin County house.

But on Sunday she could barely lift a paint can, let alone climb a ladder.

"I woke up. I felt sick to my stomach and I threw up all day," Adams said. She had diarrhea, too.

In early November, a common intestinal sickness began its yearly sweep through the Roanoke region and most other communities of the state and nation. Often called the stomach bug or stomach flu, viral gastroenteritis is a short-lived, lower abdominal infection that is impossible to prevent or cure. The malady works its grotesque way through our bodies at its own spasm speed.

Roanoke representatives of the Virginia Department of Health said the condition has sickened members of several families and some residents in two nursing homes. But the scope is believed to be wider because many sufferers don't bother to call the health department or see a doctor.

This bug flies largely under the radar of public attention, partly because it lacks the high-profile, remedy-selling opposition inspired by the common cold -- let alone the notoriety that flu derives from the annual inoculation campaign.

Laboratory testing revealed that the culprit was norovirus, a class of microbe known to cause gastroenteritis, the health department found.

"This is something we see every year," health department epidemiologist Lex Gibson said. "Once it gets in the community, it spreads pretty quickly."

If you're not already washing and gelling your hands several times a day to fight germs, it's a good habit to start. The microbe spreads through the feces and vomit of infected people. You can catch this virus from a holiday handshake, and once infected, you're likely to spend a day or two in digestive-tract misery. You probably won't die, but you might feel like you want to.

"It just put me down," said Adams, 53.

The normally active health department nurse spent the Sunday she was stricken sleeping on the couch in blue pajamas rather than doing planned home improvement projects on her day off. When she wasn't in the bathroom, she curled up with her dog, Millie.

"I just didn't want to do anything," she said.

She said she doesn't know how she got the virus. But she felt better the next day. When she returned to work, she thinks she passed the virus to a co-worker who then became sick, too.

Experts say it's possible to infect someone else even after the symptoms disappear. Some infected people never develop symptoms, which drives home the wisdom of hand-washing to ward off the colonies of unseen germs that inhabit shared surfaces.

Dr. John Gaylord, a Roanoke internal medicine specialist, said Monday by e-mail that he saw 10 patients like Adams and talked to twice that many during a recent week. That's five to 10 times the usual number.

"There appears to be an epidemic of viral gastroenteritis in the valley," Gaylord said.

Laura Rumfeldt, who manages Gaylord's three-physician office, said Gaylord didn't mean to imply an actual epidemic has received official designation from the Centers for Disease Control and Prevention. He meant a noticeable rise in gastroenteritis cases.

Why now?

Each of a handful of viruses capable of causing gastroenteritis has its own season of activity and ideal setting in which to multiply, according to the CDC. For example, in the United States, rotavirus and astrovirus infections occur during the cooler months of the year of October through April. Norovirus, the one active in the Roanoke region, thrives on the kind of close human contact that is all the more common during the holiday season. Large gatherings that revolve around food and good cheer symbolized by hugs, handshakes and festive kisses on the cheek give the infectious microbes being shed by a sick or recovering person a chance to latch on somebody else.

Gastroenteritis differs from other well-known ailments such as seasonal influenza, for which a vaccine and antiviral medicine are available. There is no guaranteed way to prevent gastroenteritis (although good hygiene helps) and no bona fide treatment for the underlying infection, although anti-nausea medicine can ease the symptoms.

Gastroenteritis is too widespread to be tracked with statistics. Many people do not see a doctor, and testing to identify the virus involved isn't routine or necessary in every case.

On the other hand, because gastroenteritis can behave like something more serious, some sufferers become concerned enough to see a doctor or visit an emergency room to have conditions such as an intestinal blockage ruled out.

The best defense is hand-washing. Hand-washing gels help, too, Gibson said.

He added this advice: "Know what you're eating and who's preparing it."

It's not only Roanokers who are parked in the lavatory with miserable symptoms. Monday, a hospital in Denbighshire, England, near Liverpool, closed three wards because an outbreak of gastroenteritis among patients, while a New Zealand newspaper reported an outbreak at a Wellington nursing home.

Last week on Thanksgiving eve, Michigan authorities confirmed a spike had sickened dozens of people in Gladwin County, the Saginaw News reported.