LATEBREAKER
Infectious Disease
Norovirus GII.17 and Sporadic Medically-Attended Acute Gastroenteritis in Oregon and Washington, 2023-2024 Mark Schmidt* Mark Schmidt Laura Tsaknaridis Holly Groom Judy Donald Sarah Vertrees Ayo Ojebode Lisa Morrow Carly Crocker Katherine Carlson Emma Viscidi
Background: When norovirus genotype GII.17 emerged in Asia in 2014, there were concerns that it would replace GII.4 as the globally predominant strain associated with acute gastroenteritis. Outside of several isolated outbreaks, this worry has largely not yet been realized. Here we describe developing results from a prospective, community-based surveillance study of medically-attended acute gastroenteritis (MAAGE) in the northwestern U.S.
Methods: Beginning November 15, 2023, we have been conducting daily recruitment of Kaiser Permanente Northwest (KPNW) patients of all ages with MAAGE diagnoses. We enrolled participants who completed a baseline survey and self-collected a stool specimen for testing at the Oregon State Public Health Laboratory (OSPHL). Norovirus detection was assayed through real-time polymerase chain reaction; Sanger sequencing was subsequently performed on specimens testing positive. We include here results received through February 23, 2024.
Results: To date, we have tested 255 stool specimens, of which 34 (13%) were positive for norovirus. Genotyping has been completed for 19 (56%): 9 (47%) were GII.17, 5 (26%) were GII.4, and one each was GI.3, GI.5, GII.3, GII.8, and GII.12; 8 are untypable and 7 are pending. Only one person with GII.17 reported contact with someone with AGE symptoms prior to their illness.
Conclusion: In this first analysis of an ongoing community-based study, the high proportion of GII.17 genotypes – and low proportion of GII.4 – detected among sporadic MAAGE cases is unexpected and notable. Our 2014-2016 similar study found 54% and 2% of 228 typable norovirus strains were GII.4 and GII.17, respectively. CDC outbreak data showing a recent doubling in outbreaks due to GII.17 further suggest the emergence of GII.17 as a cause of gastroenteritis within the U.S. Our findings underscore the importance of ongoing surveillance to characterize the genetic epidemiology of norovirus, especially to inform norovirus vaccine development.