Cases of highly contagious norovirus are climbing once again across the U.S. - just in time for the holiday travel season.
Recent data from the Centers for Disease Control and Prevention showed that the number of tests coming back positive for the potentially deadly viral infection has now reached 14 percent, doubling from just three months ago. Of the more than 2,700 tests conducted for the week of November 15, about 380 cases of norovirus were diagnosed.
The majority of cases are in the central and southern U.S., including Wyoming, Nebraska, Oklahoma, Texas and Alabama, according to electronic health records shared by Epic Research.
However, Michigan’s Wilson Middle School in Wyandotte closed last week in an effort to prevent the spread of what the state’s health department said was likely norovirus, according to Click On Detroit.
"It's just so easy to spread to each other that the best and safest thing to do is to say, 'Hey, everyone, let's take a break. Everyone go home and monitor themselves,'" Detroit Medical Center infectious disease physician Dr. Lea Monday told CBS Detroit.
The state’s weekly Disease report showed there had been 64 confirmed cases of norovirus during the past month, and a major increase in annual cases since 2021.
Although norovirus cases are ticking up nationwide, the country is still not at the record of 25 percent of tests that came back positive for norovirus in December 2024.
Last winter, dozens of outbreaks were reported within just the first week of December, with the strain known as GII.17 accounting for most cases. Some outbreaks were tied to people eating raw oysters, which can also harbor the virus.
Earlier this year, cases had been trending down. But, doctors expected a surge as the weather grows colder. While norovirus can spread throughout the year, cases are the most common between April and November.
“Norovirus classically increases in the winter months for many reasons, but the major one is that everyone is congregating indoors, especially with the holidays,” Dr. Scott Roberts, a Yale Medicine infectious diseases expert, explained in a statement.
Anyone can get infected, though children younger than five years old, older adults and people with weakened immune systems are more likely to develop severe infections.
Typical symptoms include nausea, stomach pain, fever, head and body aches, and diarrhea and vomiting that can lead to dehydration and even death.
There are 900 norovirus deaths on average each year and between 19 and 21 million illnesses.
Most people who are infected get better within 24 to 72 hours, but they can still spread the virus for two weeks after they show symptoms.
It also doesn’t take much to be exposed and, subsequently, infected. Norovirus, which is often referred to as stomach flu, can spread by sharing food or touching contaminated surfaces.
To prevent spreading norovirus or falling ill, health officials instruct people to wash their hands for at least 20 seconds often, cook shellfish thoroughly and wash fruits and vegetables, clean and disinfect contaminated surfaces and wash laundry in hot water.
“Very few norovirus particles are needed to infect a person. Other viruses need much more exposure,” said Roberts.
