Noroviruses come in a variety of flavors, and they are classified by their genogroup (GI through GVI), and their genotype, which is a number assigned based on how close certain parts of their genetic sequences are to one another. Genogroups I, II, and IV cause disease in people, and for over a decade, GII.4 viruses have caused the vast majority of norovirus outbreaks. One interesting thing happening in Jiangsu province is that there’s a norovirus causing disease outbreaks that’s not a GII.4, but a GII.17, and based on its genetic sequence, it appears to be one that hasn’t existed before.
How was this new norovirus found?
Infectious disease surveillance is a good thing to have for many reasons, but one of them is that it lets us know when something is new or abnormal. People working with one such surveillance system, the Emergent Public Health Event Information Management System (EPHEIM) in Jiangsu province, noticed a significant increase in the number of norovirus outbreaks they were having at the end of 2014, compared to the same time frame in previous years.
A group of health officials from different provincial and city-based Chinese Centers for Disease Control and Prevention, as well as different hospitals, recently published these findings in Eurosurveillance, which you can read here.
In addition to the EPHEIM system, the authors also used data on sporadic cases of norovirus that came from two additional surveillance systems: one tied to 26 hospitals in three cities that are home to over a quarter of the people in the province, and the other monitoring cases of viral diarrhea at a major pediatric hospital.
Based on the body of surveillance information, the GII.17 variant emerged in October 2014 in Jiangsu province and by February 2015, it had replaced GII.4 Sydney as the predominant cause of outbreaks in that area. More specifically, it was linked to 16 of 23 laboratory-confirmed norovirus outbreaks that had happened in Jiangsu from September 2014 through March 2015.
Why is it important to keep track of these new noroviruses?
As the old adage goes, “Know thine enemy.” For example, we know the GII.4’s have been associated with increased numbers of hospitalizations and deaths during outbreaks. Over the past decade or so, a new GII.4 norovirus has emerged every couple of years, taking the place of whatever GII.4 virus came before it as the predominant strain. For example, before GII.4 Sydney hit the scene in 2012, we had GII.4 New Orleans to blame for much of the world’s norovirus outbreaks. At least for the GII.4’s, when a new one emerges, we also often see an increase in the number of outbreaks, probably because it’s something our bodies haven’t encountered before.
In contrast, we know considerably less about the GII.17’s since they have not been a major player, but people are keeping an eye on them. In recent years, GII.17 noroviruses have been identified elsewhere in China, the U.S., and Kenya, just to give a few examples.
Will this new norovirus become as prevalent as GII.4 Sydney is now?
No one can say, and only time will tell. Sometimes new noroviruses pop up in an area and they don’t go very far, while others become the new name in norovirus outbreaks. We’ll certainly write about it here if things stay interesting.
Original article citation:
Fu, J., Ai, J., Jin, M., Jiang, C., Zhang, J., Shi, C., Lin, Q., Yuan, Z., Qi, X., Bao, C., Tang, F., Zhu, Y. 2015. Emergence of a new GII.17 norovirus variant in patients with acute gastroenteritis in Jiangsu, China, September 2014 to March 2015. Eurosurveillance, 20(24).