To investigate nationwide severe fever with thrombocytopenia syndrome virus (SFTSV) infection status, we isolated SFTSVs from patients with suspected severe fever with thrombocytopenia syndrome (SFTS) in 207 hospitals throughout South Korea between 2013 and April 2017. A total of 116 SFTSVs were isolated from 3137 SFTS-suspected patients, with an overall 21.6% case fatality rate. Genetic characterization revealed that at least 6 genotypes of SFTSVs were co-circulating in South Korea, with multiple reassortments among them. Of these, the genotype B-2 strains were the most prevalent, followed by the A and F genotypes. Clinical and epidemiologic investigations revealed that genotype B strains were associated with the highest case fatality rate, while genotype A caused only one fatality among 10 patients. Further, ferret infection studies demonstrated varying clinical manifestations and case mortality rates with different strains of SFTSV, which suggests this virus could exhibit genotype-dependent pathogenicity.

Severe fever with thrombocytopenia syndrome (SFTS) is caused by SFTS virus (SFTSV). Although SFTS originated in China, it is an emerging infectious disease with prevalence confirmed in Japan, Korea, and Vietnam. The full-length genomes of 51 Korean SFTSV isolates from 2013 to 2016 were sequenced, and the sequences were deposited into a public database (GenBank) and analyzed to elucidate the phylogeny and evolution of the virus. Although most of the Korean SFTSV isolates were closely related to previously reported Japanese isolates, some were closely related to previously reported Chinese isolates. We identified one Korean strain that appears to have resulted from multiple inter-lineage reassortments. Several nucleotide and amino acid variations specific to the Korean isolates were identified. Future studies should focus on how these variations affect virus pathogenicity and evolution.

Noroviruses are a leading cause of acute gastroenteritis worldwide, with a particularly high burden among children under five years of age. We analyzed nationwide surveillance data from EnterNet-Korea collected between 2019 and 2024—covering both the pre- and post-COVID-19 pandemic periods—to assess norovirus detection rates and genotype distribution. Noroviruses were detected by RT-qPCR, and dual genotyping of capsid (G) and polymerase (P) types was performed by sequencing the ORF1–2 junction region. Among the 67,159 specimens tested, 8.4% (n = 5652) were norovirus-positive, with the highest prevalence observed in children aged 0–5 years (19.9%). In this age group, genotyping was successful in 72.4% (2633/3635) of positive cases, identifying 30 distinct genotypes (GI: 9; GII: 21). The most common strains were GII.4[P31] (38.1%), GII.4[P16] (27.1%), and GII.2[P16] (10.4%), with substantial year-to-year variation. Notably, the emergence of GII.17[P17] in late 2024 indicates shifting genotype dynamics, underscoring the need for strengthened surveillance and reconsideration of vaccine strain selection. To our knowledge, this is the first nationwide dual-typing study in Korea encompassing the COVID-19 pandemic era. These findings provide essential baseline data for integration into global surveillance systems and inform future vaccine development and public health strategies.

The equine-like G3 rotavirus is a reassortant strain in which an animal-derived G3 genotype has recombined with a human-origin genetic backbone. Recently, this strain has spread across Asia and Europe. In this study, the VP7 and VP4 genes, along with the genomic backbone of 39 G3P[8] rotavirus strains detected in South Korean children with acute gastroenteritis between 2017 and May 2025, were analyzed. All strains harbored the equine-like G3 genotype for the VP7 gene, and segmental genotyping of VP7, VP4, and VP6 suggested that these strains possessed a DS-1-like genetic backbone (I2-R2-C2-M2-A2-N2-T2-E2-H2). All VP4 genes were confirmed as P[8]. Phylogenetic analysis revealed that these strains clustered with previously reported equine-like G3 strains from various regions, including East Asia. Although individual vaccination records were not available in the EnterNet surveillance data, the overall detection rate of rotavirus infection has declined following vaccine introduction. Nevertheless, equine-like G3P[8] strains have continued to appear sporadically in Korean children, underscoring the importance of ongoing genomic surveillance in the post-vaccine era. Overall, these findings indicate that equine-like G3P[8] strains with a DS-1-like backbone have been circulating for several years in the pediatric population in South Korea, offering important insights into vaccine effectiveness and the surveillance of reassortant rotaviruses.

Objectives: On February 16, 2022, 12 cases of hepatitis E virus (HEV) infection were reported in a food manufacturing factory in Korea. The aim of this study was to identify additional cases and to determine the source of this HEV outbreak.Methods: This study was an in-depth investigation of 12 HEV immunoglobulin M (IgM)-positive cases and their demographic, clinical, and epidemiological characteristics. On-site specimens were collected from the environment and from humans, and a follow-up investigation was conducted 2 to 3 months after the outbreak.Results: Among 80 production workers in the factory, 12 (15.0%) had acute HEV infection, all of whom were asymptomatic. The follow-up investigation showed that 3 cases were HEV IgM-positive, while 6 were HEV IgG-positive. HEV genes were not detected in the HEV IgM-positive specimens. HEV genes were not detected in the food products or environmental specimens collected on-site. HEV was presumed to be the causative pathogen. However, it could not be confirmed that the source of infection was common consumption inside the factory.Conclusion: This was the first domestic case of an HEV infection outbreak in a food manufacturing factory in Korea. Our results provide information for the future control of outbreaks and for the preparation of measures to prevent domestic outbreaks of HEV infection.

Recently, the norovirus GII.13[P16] strain, the source of which has not been identified, was detected in epidemiological investigation samples from four regions in South Korea. The norovirus GII.13 genotype is rare worldwide. In this case, the causative pathogen was not identified in the food, and the epidemiological characteristics of the transmission route could not be confirmed. The P2 domain of norovirus is a hypervariable region, and analyzing its sequence analysis is an important approach for identifying transmission routes and epidemiological relationships. Cluster analysis confirmed that the capsid region of the norovirus GII.13 strain detected in samples from the four regions showed some differences from that of the GII.13 strain reported in Germany. Additionally, the differences among the strains from the four regions in the capsid and the nucleotide sequence of the P2 domain were identical. Our findings suggest that the source of contamination in patients in the four regions was the same.