Norovirus cases are up. Should travelers worry?

With norovirus cases on the upswing, some travelers may be rethinking their plans. But there's no need to worry more than usual.

Norovirus cases have risen throughout the U.S. recently, but the numbers are not unusual, according to the Centers for Disease Control and Prevention. 

"The most recent CDC data collected from the NoroSTAT program and the National Respiratory and Enteric Virus Surveillance System show that reported norovirus outbreaks and reported cases from both state health departments and clinical laboratories are increasing, but remain within the expected range for this time of year," a CDC spokesperson told USA TODAY in an email.

The U.S. had a three-week average positivity rate of 16.7% as of late February, according to National Respiratory and Enteric Virus Surveillance System data on the agency's website, up from 14.6% about a year earlier.

"Prevention measures implemented during the COVID-19 pandemic were likely effective in preventing norovirus outbreaks," the spokesperson added. "As pandemic restrictions have relaxed, the number of norovirus outbreaks has returned to levels similar to pre-pandemic years."

Is everyone you know sick?:Explaining winter's early rush of illness – and if it will continue

Cruise ship medical facilities:What happens if you get sick or injured (or bitten by a monkey)

Other parts of the world have seen more dramatic increases. In England, lab reports of the virus are up 66% from the average this time of year, the U.K. Health Security Agency said this month.

"I think it's worth knowing the epidemiological situation wherever you're traveling to, like it's worth knowing the weather report where you're traveling," said Ben Lopman, a professor of epidemiology at Emory University’s Rollins School of Public Health. "But ... there are things you can do to reduce your risks."

What is norovirus?

Norovirus is a virus that causes diarrhea and vomiting, according to the CDC's website. The illness is highly contagious, and people can get infected by interacting directly with someone who is infected, consuming food or water that is contaminated, or putting unwashed hands in their mouths after touching contaminated surfaces.

Other symptoms of norovirus can include stomach pain, nausea, headache, body aches and fever.

"You can get norovirus illness many times in your life because there are many different types of noroviruses," the CDC said on its website. "Infection with one type of norovirus may not protect you against other types."

There's no particular medicine to treat norovirus, but the agency recommends drinking lots of fluids to prevent dehydration.

Should travelers be worried about catching norovirus?

Lopman said that "every winter, COVID years aside," there is a surge in norovirus cases.

Traveling – particularly internationally – puts people at increased risk of contracting illnesses like norovirus, however, due in part to changes in behavior.

"We interact with different people and more people and eat different foods," Lopman said. "And also, we're potentially exposed to pathogens, bacteria, viruses that are not so common often in our home countries."

And while norovirus is often associated with cruise ships, he said those represent a "tiny minority of norovirus outbreaks," while the vast majority are in health care settings like nursing homes. 

"The other thing is that they're pretty easy to recognize on a cruise ship: people come together, people start getting sick, we'll see that there's a cluster of cases," he said. "That may not be true if, for example, people are eating contaminated food at a restaurant, but then they're all going home and going their separate ways."

Norovirus cases also plummeted on cruises in the wake of the pandemic.

How can travelers protect themselves?

Lopman said travelers protect themselves by washing their hands frequently with soap and water. "Those alcohol-based hand sanitizers don't work very well for norovirus, so soap and water is really the way to go," he said.

When cooking, the CDC recommends washing vegetables and fruits carefully and cooking oysters and other shellfish to a minimum internal temperature of 145 degrees. "Be aware that noroviruses are relatively resistant to heat," the agency said on its website. "They can survive temperatures as high as 145 (degrees Fahrenheit). Quick steaming processes that are often used for cooking shellfish may not heat foods enough to kill noroviruses."

Planes carry medical kits:Here's why you may not rely on them in an emergency

FDA sends warning to American Cruise Lines:Letter came after guests contracted Legionnaires' disease

Lopman also recommended those infected isolate themselves. Most people recover within three days, but he noted that they can remain infectious even after they feel better, making hand-washing especially important.

Nathan Diller is a travel reporter based in Tennessee. You can reach him at ndiller@usatoday.com