If it seems like everyone you know has the stomach flu, it’s not just in your head.
Rates of norovirus – commonly known as the stomach flu – are about twice as high as they were between 2021 and 2024 and nine times higher than during the first year of the pandemic.
There were 91 outbreaks of the virus in the week ending Dec. 5, the most recent date with available data, and state-level trends suggest that number will continue to rise.
This time last year, health departments in more than a dozen states reported just 41 outbreaks.
And during the Covid pandemic, the CDC reported no more than 10 outbreaks per week, which infectious disease experts attribute to masking, social distancing, isolation and frequent handwashing.
Norovirus causes severe diarrhea and vomiting, which can lead to life-threatening dehydration. It spreads through contact with germs from an infected person’s vomit or feces, contaminated food, shared utensils, or surfaces they have touched.
The virus infects about 21 million Americans annually and sends about 2 million to the doctor’s office or emergency care.
Although most people recover within a few days, the virus kills about 900 people every year, mostly adults 65 and older.
Outbreaks are most common around this time of year due to an increase in the number of people gathering in groups for holiday festivities, traveling and staying warm indoors, where pathogens can easily spread.
This year’s rapid rise can also be attributed to pandemic-era safety measures such as the widespread use of hand sanitizer, masking and isolation.
Immunity to norovirus only lasts strong for a few years, so by the time society cast aside these safety measures, immunity had disappeared for the entire population.
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The CDCs latest figures support this theory. From 2012 to 2020, the US documented approximately 1,500 norovirus outbreaks; over the next five years there were almost 2,400 outbreaks. More than 400 were recorded in 2024 alone.
Washing your hands can make the difference between normal health and a sleepless night hunched over the toilet.
Dr. Celine Gounder, an infectious disease specialist at New York University’s Grossman School of Medicine, said NPR: ‘We have seen several types of gastroenteritis decrease during the pandemic because people were also washing their hands.
“And once there was a return to some sort of more normal disgusting behavior, we saw it increase again.”
Symptoms of norovirus – nausea, vomiting and diarrhea – typically appear 12 to 48 hours after exposure. Most people recover within a few days, but the virus claims about 900 lives each year, mostly among adults aged 65 and over
Doctors say illness can be prevented by washing your hands thoroughly with soap and water for at least 20 seconds, washing produce before eating it, disinfecting countertops, avoiding people who are contaminated, and cooking seafood to at least 145 degrees.
Some scientists have speculated that this year’s surge of norovirus cases could be caused by a new strain against which people have no pre-existing immunity.
Lee-Ann Jaykus, a microbiologist at North Carolina State University who leads NoroCORE, a multi-federal food virology collaboration, said that while the CDC’s genetic analyzes of circulating noroviruses have not revealed significant changes this season , the potential emergence of a new species is a major concern for many experts.
She told me Vox: ‘I can guarantee you that my colleagues at the CDC are doing a lot of sequencing now to find out if there is a new strain, but it is still too early to say if there is one.’
Symptoms of norovirus – nausea, vomiting and diarrhea – occur quickly, within 12 to 48 hours after exposure.
Dehydration is a big problem. Frequent vomiting and diarrhea can quickly cause the body to lose fluid and electrolytes, which can lead to dangerously low blood pressure, reduced blood flow to vital organs, and an electrolyte imbalance that can be harmful to the heart and muscles.
An electrolyte imbalance can also lead to seizures and, in some cases, loss of consciousness.
Hand sanitizers alone cannot kill the virus particles on the skin. Therefore, doctors strongly recommend washing hands often.