Will norovirus surge early again this year? CDC urges tracking of new strain.
The latest report from the Centers for Disease Control and Prevention suggests that a new strain of norovirus may have disrupted the usual seasonal pattern of outbreaks. In previous years, norovirus outbreaks typically increased around December, marking the start of the season for the virus. However, last year saw a different trend as a new strain called GII.17 emerged, leading to a record wave of outbreaks starting as early as October.
According to the CDC researchers, continued surveillance is necessary to determine if the GII.17 genotype will remain dominant and if the norovirus season will continue to start earlier than in previous years. While outbreaks have since slowed to normal levels, GII.17 has been identified in more than 75% of outbreaks in the U.S., displacing the previously dominant GII.4 strain. This shift raises questions about whether the norovirus season could begin early again.
Similar trends were observed in other countries, with England reporting levels of norovirus activity more than double recent seasons, and GII.17 being the most frequently reported genotype. In Japan, a steep wave of infectious gastroenteritis, mainly from norovirus, peaked later than usual and remained above recent years.
Miranda de Graaf, a scientist at Erasmus University Medical Center in the Netherlands, noted that while GII.17 replaced GII.4 last year, it is uncertain if this shift will last or if GII.17 will be the predominant strain in the next winter season. Benjamin Lopman, an epidemiology professor at Emory University, explained that shifts in norovirus strains occur when new variants evade existing immunity, leading to more frequent outbreaks earlier in the season.
Looking ahead, Lopman anticipates that outbreak patterns will likely return to normal levels and seasonal patterns in the coming years, although predicting the behavior of these viruses remains challenging.
For more updates on public health issues, stay tuned to CBS News.
