If you've ever dealt with a nasty stomach bug, chances are you’ve encountered the norovirus, even if you didn’t know its name.

“When someone shows up at the E.R. or their doctor’s office complaining of vomiting, nausea, or diarrhea, there’s a 10-25% chance it’s norovirus,” said Territorial Epidemiologist Patrick Sotto.

Right now, this highly contagious virus is on the rise across the U.S.

The CDC recently reported 91 norovirus outbreaks in the week of Dec. 5th alone. More than double the number from the same week in the past three years.

But what’s happening here?

Patrick Sotto with the Guam Department of Public Health said local health officials monitor norovirus through cases of acute gastroenteritis since the virus fits under the generalized syndrome.

“There’s nothing concerning right now, but that doesn’t mean we shouldn’t take proactive measures,” said Sotto.

So, what can you do?

The simplest and most effective step is washing your hands properly. That means scrubbing with soap and water for 20 seconds, about as long as it takes to sing the ABC’s.

This small effort makes a big difference, as person-to-person contact accounts for 90% of the norovirus outbreak transmission mode.

“It usually starts with contaminated food products, and then it becomes very easy to spread. Once it hits that human reservoir—once someone gets infected—it becomes very easy to spread, especially if we’re not taking those precautions,” added Sotto.

Following good hygiene practices can protect you and those most at risk, including young children under 5, the elderly, and people with weakened immune systems. and don’t forget—even after you start feeling better, you can still spread the virus for up to two weeks.

And while there are no signs of concern now, Public Health officials are keeping a close watch.

Chief Medical Officer Dr. Robert Leon Guerrero emphasized the importance of staying ahead of the virus.

“Wash your hands well, and in this particular case, not so much hand sanitizer, but washing your hands with soap and water, especially if you’re going to prepare a meal, taking care of people at childcare or senior citizen centers, and the hospitals too—to practice good sensible washing technique,” said Dr. Leon Guerrero.