Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Nov 21;17(12):1530.
doi: 10.3390/v17121530.

Delayed Emergence of Norovirus GII.17 in Finland: Foodborne Outbreaks Reported During the 2024/25 Season

Haider Al-Hello  1   2 , Ruska Rimhanen-Finne  1 , Carita Savolainen-Kopra  1
Affiliations

Delayed Emergence of Norovirus GII.17 in Finland: Foodborne Outbreaks Reported During the 2024/25 Season

Haider Al-Hello et al. Viruses. .

Abstract

During the 2024/25 season, Finland experienced a delayed emergence of norovirus genotype GII.17, which had already become prevalent in several European countries and the United States during the previous season, 2023/24. In Finland, GII.17 was confirmed in three foodborne outbreaks and five sporadic cases, marking the highest number of detections to date. These cases were geographically distributed across southern, western, and northern Finland, indicating widespread circulation. Retrospective analysis of national surveillance data from 2014 to 2025 revealed that GII.17 had been detected sporadically in earlier years but never at this scale. The emergence of GII.17 coincided with a continued presence of GII.4 [P16], the previously dominant genotype. Phylogenetic analysis showed that Finnish GII.17 strains clustered with recent international strains, suggesting introduction from abroad. The findings highlight the importance of sustained genotyping and international surveillance to detect emerging norovirus variants and inform public health preparedness in Finland.

Keywords: GII.17; norovirus; phylogenetic analysis; retrospective analysis.

PubMed Disclaimer

Conflict of interest statement

We declare no conflicts of interest.

Figures

Figure 1
Figure 1
Monthly reported norovirus cases in Finland from the 2015/16 to 2024/25 seasons. This figure illustrates a biennial pattern of norovirus epidemics in Finland, with notable peaks in the 2016/17, 2018/19, 2021/22, and 2023/24 seasons. The numbers on the peaks indicate the total number of cases at each peak. The total number of cases for the entire season is mentioned below. GII.17 refers to the years in which this genotype was detected. A significant decline in cases is observed during the COVID-19 pandemic years (2019/20 and 2020/21); three years after the pandemic, norovirus case numbers were like those seen in norovirus epidemic years before the pandemic began. Notably, GII.17 norovirus has been detected in both high-incidence and low-incidence seasons, indicating its persistent circulation regardless of overall epidemic intensity. The 2024/25 season marks the highest number of GII.17 detections to date, in both outbreaks and sporadic cases. NR = no record.
Figure 2
Figure 2
(A) Phylogenetic analysis of ten Finnish GII.17 VP1 sequences (200–290 bp) and 77 corresponding global sequences. (B) Phylogenetic analysis of 42 Finnish GII.P17 polymerase sequences (170–260 bp) and 100 corresponding global sequences.
Figure 2
Figure 2
(A) Phylogenetic analysis of ten Finnish GII.17 VP1 sequences (200–290 bp) and 77 corresponding global sequences. (B) Phylogenetic analysis of 42 Finnish GII.P17 polymerase sequences (170–260 bp) and 100 corresponding global sequences.
See this image and copyright information in PMC

References

    1. Platts-Mills J.A., Taniuchi M., Uddin M.J., Sobuz S.U., Mahfuz M., Gaffar S.M.A., Mondal D., Hossain M.I., Islam M.M., Ahmed A.M.S., et al. Association between enteropathogens and malnutrition in children aged 6–23 mo in Bangladesh: A case-control study1, 2, 3. Am. J. Clin. Nutr. 2017;105:1132–1138. doi: 10.3945/ajcn.116.138800. - DOI - PMC - PubMed
    1. Finnish Legislation. [(accessed on 18 November 2025)]. Available online: https://www.finlex.fi/fi/lainsaadanto/2011/1365.
    1. Vinjé J., Hamidjaja R.A., Sobsey M.D. Development and application of a capsid VP1 (region D) based reverse transcription PCR assay for genotyping of genogroup I and II noroviruses. J. Virol. Methods. 2004;116:109–117. doi: 10.1016/j.jviromet.2003.11.001. - DOI - PubMed
    1. Norovirus Typing Tool Version 2.0. [(accessed on 18 November 2025)]. Available online: https://mpf.rivm.nl/mpf/norovirus/typingtool/
    1. Lindesmith L.C., Kocher J.F., Donaldson E.F., Debbink K., Mallory M.L., Swann E.W., Brewer-Jensen P.D., Baric R.S. Emergence of Novel Human Norovirus GII.17 Strains Correlates with Changes in Blockade Antibody Epitopes. J. Infect. Dis. 2017;216:1227–1234. doi: 10.1093/infdis/jix385. - DOI - PMC - PubMed

LinkOut - more resources