Scientists call this winter’s dominant norovirus strain GII.17.[P17]. About 7 in 10 patient samples from norovirus outbreaks have tested positive for the new strain so far this season, according to data from a network of public health laboratories called CaliciNet.
“It’s too early to tell if this strain is linked to more severe norovirus disease, but it’s possible that waning immunity in the population may have contributed to the initial spike in seasonal outbreaks of the virus,” said John Vanje, director of the CDC’s CaliciNet system. There is a reason.” CBS News in an email.
All previous waves of norovirus in the U.S. since 2012 have been dominated by a different strain, which scientists call GII.4, Vinje said. This season, only about 7% of norovirus outbreaks have been attributed to this GII.4 strain.
Vinje said the GII.17 strain was behind the “ubiquitous” outbreak across the country Highly contagious including viruses Cruise ship spread out
The CDC tracked at least six norovirus outbreaks on ships last month, the most reported that month in more than a decade.
Norovirus is the most common cause. Food borne illness In the U.S. and almost always across the country beginning during the winter months.
Many cases resolve on their own without the need for tests or treatment by doctors, making it impossible to know how many Americans are sick. However, virtually all data from virus trackers indicates that norovirus is on the rise across the country.
Rates of positive norovirus tests from a diverse CDC network of laboratories have reached the highest weekly level on record in years. Norovirus rates Data from Testing company BioFire Diagnostics is also now above previous seasonal peaks.
in dirty water, Samples WastewaterSCAN collected is “high” for norovirus at nearly all sites the firm monitors nationwide.
Although versions of GII.17 have been circulating for decades, only in recent years has the strain caused large waves of infection. Some parts of Europe last year reported a “sudden increase” in GII.17. Japan And China reported their first waves of stress since 2014.
The CDC reports that it has seen an increase in GII.17 cases. Last seasonAlthough it remained in the minority of all norovirus outbreaks in the United States at that time.
Does GII.17 cause more or worse norovirus cases?
Additional studies will also be needed to determine whether GII.17 is contributing to differences in the severity of norovirus infections. something Previous changes Viruses have emerged without causing new or significantly worse symptoms.
“What we’re seeing has happened before for noroviruses. Noroviruses are very diverse,” said Marion Koopmans, head of the Erasmus MC Department of Virology.
Koopmans, who oversees the Global Consortium of Norovirus Researchers, cautioned that there are still gaps worldwide in data tracking norovirus cases. More studies are also needed to prove whether there is a real increase in stress-related illnesses.
“There is insufficient surveillance (in my opinion) to really make the case that this is causing an increase in the number of cases, because we have so many norovirus infections every winter and surveillance is so complicated,” Koopmans said. is,” Koopmans said.
When the latest GII.4 strain, called the Sydney variant, emerged in 2012, preliminary data suggested it had fueled outbreaks. The CDC later reported data from hospitals showing that it did not actually lead to significantly more or worse norovirus infections.
“Thus, the observed increase in outbreak activity during the 2012-13 season represents random seasonal and state variation rather than a direct result of GII.4 Sydney emergence,” CDC scientists concluded at the time. What did
Health officials in Wisconsin said earlier this month they’ve seen a record number of norovirus outbreaks, but told CBS News they don’t believe that makes a big difference in the symptoms or length of the illness. is
“It doesn’t change any recommendations about prevention or spread. It just means that we have a strong outbreak season and therefore really need to wash hands, stay home when sick and stay healthy. “There is an opportunity to push for at least 48 hours after conception,” said Elizabeth Goodset. A spokesman for the Wisconsin Department of Health Services, in an email.