Cases of nasty stomach bugs caused by norovirus appear to be skyrocketing in Massachusetts this season. The number of laboratory-confirmed cases more than tripled between 2022 and 2024, state health department data show.
But experts point out that the increase could be a misleading confluence of factors, including testing advances that emerged from the COVID-19 pandemic.
In 2022, the state recorded 678 confirmed cases of norovirus, which jumped to 1,252 in 2023 and an annual count of 2,080 cases in 2024.
But the state’s department of public health and outside experts say that what looks like a major increase may have more to do with a jump in testing over the last few years.
“It is possible that the uptick may be partially due to increased use of syndromic testing panels, along with some artificial increase due to false positivity reported by some panel manufacturers in recent years,” DPH spokesperson Omar Cabrera said in a statement.
It’s long been believed to be one of the most common causes of foodborne illness in the United States, and until recently, testing was difficult to nail down.
But advances in testing and wastewater detection are making it easier to detect the presence of norovirus than it has ever been before, said Ruanne Barnabas, who leads the infectious diseases division at Massachusetts General Hospital.
“We’re seeing data that could have several explanations,” Barnabas said. “Testing is easier and more widely available, and we test for norovirus now as part of a whole panel of tests. We’re also getting together more and perhaps there’s more transmission.
“We don’t know yet if this is really something out of the ordinary,” she added.
Wastewater data in Greater Boston shows that levels of norovirus are “high” — and are at their highest since that tracking began in late 2022.
Wastewater data was introduced as a way to detect norovirus after its initial use to detect COVID-19 during the pandemic, “but it’s not something we’ve been doing for decades,” Barnabas said. “It’s something new that we have extended since the pandemic, and it’s not uncommon for this time of year to see a rise in levels.”
The virus causes a gastrointestinal illness when even small amounts of certain viral strains are ingested, leading to gastrointestinal issues, fever, chills and dehydration.
“It’s a very infectious virus. You just need a small dose to acquire the infection,” Barnabas said. “The virus lives on surfaces and it’s not killed by alcohol-based hand sanitizers, so this is very commonly transmitted from hand to mouth and the best thing to do is just wash your hands with hot water and soap.”
Clinical trials began in 2024 for an mRNa vaccine to prevent norovirus infection, just one of several advancements that emerged after the height of COVID-19.
“It’s an exciting time in science because we can do these things that, even 15 years ago, seemed really hard,” Barnabas said. “Our technology is so good now that we can design antigens in a very specific fashion and test them and really bring them to bear on human health in a way that can reduce suffering.”
