Introduction:The ongoing evolution of porcine epidemic diarrhea virus (PEDV) continues to significantly threaten the swine industry, necessitating extensive surveillance for the emergence of new PEDV variants in the field. Although genotype 2b (G2b) PEDV strains have been predominant in Korea since 2013, this study reports PEDV strains distinct from Korean G2b strains from two Korean pig farms experiencing severe diarrhea and mortality in sucking piglets. Methods:We report the first isolation and detailed characterization of a PEDV strain, designated KPED2021-1, from clinical specimens collected during outbreaks. Results:At the whole-genome level, KPED2021-1 demonstrated over 99G2c PEDV strains, which exhibit substantial genetic variation in China. In contrast, it shared 96.6%-98.7% homology with PEDV strains from Korea and other countries. Furthermore, KPED2021-1 showed greater nucleotide divergence in the NSP1, ORF3, and N genes from Korean and other global PEDV strains, while remaining more closely related to Chinese G2c strains in these regions. The amino-acid sequence of the spike (S) protein from KPED2021-1 was compared with that of the S protein from the Korean G2b strains, revealing 27 amino- acid substitutions and a unique deletion (11197). In experimental infection of suckling piglets, severe clinical symptoms and histopathological lesions were observed, resulting in a 100% mortality rate, suggesting that the KPED2021-1 strain is virulent. Discussion/Conclusion:This is the first report on the emergence of a G2c-subtype PEDV closely related to Chinese variants in Korea, and the isolate may serve as a useful reference strain for future vaccine development and cross-protection studies.

Although porcine sapelovirus (PSV) is generally subclinical, it can cause a wide range of clinical signs in some individuals, including respiratory distress, acute diarrhea, pneumonia, skin lesions, reproductive failure, and neurological diseases. In this study, we investigated the prevalence and genotype of PSV isolated from domestic pigs and wild boars in Korea. We also analyzed potential recombination events, and assessed the pathogenicity of the virus through animal experiments. In wild boars, the prevalence of PSV antibodies decreased slightly (by 1.8%) over 5 years (from 2019 to 2024); however, prevalence increased significantly (by 17.8%) in breeding sows. In samples from animals with diarrhea and respiratory clinical signs, the prevalence of PSV alone was 21.1%, whereas the prevalence of PSV mixed with other pathogens was also 21.1%. The whole genome of the PSV/Goryeong/KR-2019 strain isolated from a piglet with diarrhea was closely related to the Jpsv447 strain isolated in Japan in 2009, and recombination analysis predicted that the PSV/Goryeong/KR-2019 strain was generated by genetic recombination between the KS05151 strain and the Jpsv447 strain. However, when the PSV/Goryeong/KR-2019 strain was orally administered to 5-day-old suckling pigs, diarrhea clinical signs were mild, and no significant changes were observed in villus height and ridge depth in the duodenum, jejunum, or ileum. In addition, no neurological clinical signs were observed when the isolated virus was administered to 130-day-old pigs, and no specific lesions were found upon histopathological examination of brain tissue. In conclusion, PSV/Goryeong/KR-2019 appears to be a weakly pathogenic virus that does not cause severe diarrhea in suckling pigs, and does not cause neurological clinical signs in fattening pigs. Therefore, it is presumed that most PSVs detected in Korean pig farms are weakly pathogenic strains.

Porcine reproductive and respiratory syndrome virus type 2 (PRRSV-2) continues to pose a major threat to global swine health. In South Korea, the co-circulation of endemic strains and repeated introductions of foreign variants has led to a complex viral landscape. This study analyzed 907 non-redundant ORF5 sequences from Korean field isolates (2018–2024), derived from 1,305 compiled sequences after removing near-duplicates at 99.9

Surrogate viruses provide a safe and scalable alternative for evaluating disinfectant efficacy when access to high-risk pathogens is restricted. This study evaluated the potential of Modified Vaccinia Ankara (MVA) virus, which can be handled under BSL-1/2 conditions, as a surrogate for avian influenza virus (AIV), foot-and-mouth disease virus (FMDV), and African swine fever virus (ASFV). A total of 64 commercially available disinfectants—classified into four major chemical groups: quaternary ammonium compounds, oxidizing agents, PPMS-based formulations, and organic acids—were tested in suspension assays using a ≥4 log reduction as the efficacy criterion. MVA showed the strongest predictive performance for FMDV (r = 0.671, AUC = 0.83), supporting its use for both binary classification and approximate quantitative prediction. Although its correlation with ASFV was weaker (r = 0.175), the classification performance remained moderate (AUC = 0.78), indicating conditional applicability. While MVA exhibited no meaningful correlation with AIV, its higher chemical resistance meant that disinfectants effective against MVA were consistently effective against AIV. These results support the use of MVA as a conservative exclusion tool for fragile viruses. Overall, the findings demonstrate that MVA can serve as a practical surrogate virus for disinfectant efficacy testing against FMDV, ASFV, and AIV, with application strategies tailored to each virus’s characteristics.

African swine fever virus (ASFV) is a highly virulent DNA virus that has spread globally since its introduction into Georgia in 2007, causing substantial economic losses in the swine industry. In the absence of an effective vaccine, chemical disinfection remains a key strategy for disease control. However, in cell-based disinfectant efficacy testing, distinguishing between disinfectant-induced cytotoxicity and virus-induced cytopathic effects (CPEs) remains a major challenge, leading to the potential misinterpretation of results. To address this, we developed a multi-step analytical framework to differentiate CPEs from cytotoxicity using a Vero cell-adapted ASFV strain. Virkon® S was tested at three dilutions—375×, 275× (manufacturer-recommended), and 175×—and evaluated through CPE observation, lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, and antigen detection via lateral flow immunoassay (p30) and immunofluorescence (p54). Notably, the 375× dilution achieved effective viral inactivation with significantly lower cytotoxicity, demonstrating that this framework can facilitate a more refined determination of disinfectant working dilutions. Furthermore, increased p30 signals after disinfection and the observation of lower cytotoxicity in virus-plus-disinfectant groups compared to disinfectant-only groups highlight the complexity of virus-disinfectant interactions and the potential for misinterpretation. This study provides a standardized and interpretable strategy for assessing ASFV disinfectant efficacy and offers a practical basis for evaluating other enveloped viruses in future disinfection studies.

Orthopneumoviruses have been found in humans and various animal hosts, including mice, cattle, dogs, and swine, in several countries, but have rarely been found in cats, with the only report being from the United States in 2010. This study is the first to detect feline orthopneumovirus (FPnV) in domestic cats in South Korea and the first to characterize the complete genomic sequence of the virus worldwide. FPnV was detected in 7 of 318 feline respiratory clinical samples, resulting in a detection rate of 2.2%. A complete genome sequence and a G gene sequence were successfully obtained from two FPnV-positive samples. Sequence analysis of these Korean FPnV strains (KFPnV-2201 and KFPnV-2202) showed the highest homology with the Korean swine orthopneumovirus (SOV) strain, KSOV-2201, which was recently identified in domestic pigs in South Korea. Surprisingly, KFPnVs showed relatively low homology with the FPnVs previously reported in the United States. As a result of phylogenetic analysis, FPnV strains previously reported in the United States were classified as genogroup 1, while two FPnV strains in Korea were classified as genogroup 2, along with four strains from the United States and Korea, and two canine orthopneumovirus (CPnV) strains in China. These results suggest that genetically diverse FPnV strains may be widely distributed globally, highlighting the need for continuous surveillance of the virus. Additionally, the high genetic homology among the viruses derived from different hosts, including cats, dogs, and pigs, suggests the possibility of cross-species transmission. These findings provide evidence that genetically diverse orthopneumoviruses are circulating in various animal hosts and that these viruses may be evolving through cross-species transmission. Therefore, further extensive studies are needed to understand the epidemiology, pathogenesis, and genetic evolution of FPnV.

Porcine respiratory coronavirus (PRCV) is a member of the species Alphacoronavirus 1 within the genus Alphacoronavirus of the family Coronaviridae. A few studies have been conducted on the prevalence of PRCV since its first identification in 1997, but there have been no recent studies on the prevalence and genetic characterization of the virus in Korea. In this study, the seroprevalence of PRCV was determined in Korean pig farms using a commercially available TGEV/PRCV differential enzyme-linked immunosorbent assay kit. The farm-level seroprevalence of PRCV was determined to be 68.6% (48/70), similar to previous reports in Korea, suggesting that PRCV is still circulating in Korean pig herds nationwide. Among the 20 PRCV-seropositive farms tested in this study, PRCV RNAs were detected in 17 oral fluid samples (28.3%) from nine farms (45.0%), while TGEV RNAs were not detected in any sample. To investigate the genetic characteristics of Korean PRCV strains, genetic and phylogenetic analyses were conducted on PRCV spike gene sequences obtained in this study. The three Korean PRCV strains (KPRCV2401, KPRCV2402, and KPRCV2403) shared 98.5–100% homology with each other and 96.2–96.6% and 91.6–94.5% homology with European and American strains, respectively. A 224-amino acid deletion was found in the S gene of both Korean and European PRCVs but not in that of American PRCVs, suggesting a European origin for Korean PRCVs. Phylogenetic analysis showed that Korean PRCVs are more closely related to European PRCVs than American PRCVs but clustered apart from both, suggesting that Korean PRCV has evolved independently since its emergence in Korean PRCVs. The results of this study will help expand knowledge on the epidemiology and molecular biology of PRCV currently circulating in Korea.

Parvoviruses in the family Parvoviridae are currently classified into three subfamilies, Densovirinae, Parvovirinae, and Hamaparvovirinae, members of which infect non-vertebrate, vertebrate, and both non-vertebrate and vertebrate hosts, respectively.The subfamily Parvovirinae is divided into eleven genera based on the recently revised taxonomy: Amdoparvovirus, Artiparvo-

Since 2014, periodic outbreaks of high pathogenicity avian influenza (HPAI) caused by clade 2.3.4.4 H5 HPAI virus (HPAIV) have resulted in huge economic losses in the Korean poultry industry. During the winter season of 2016-2017, clade 2.3.4.4e H5N6 HPAIVs classified into 5 subgroups (C1-5) were introduced into South Korea. Interestingly, it was revealed that the subgroup C2 and C4 viruses were predominantly distributed throughout the country, whereas detection of the subgroup C3 viruses was confined in a specific local region. In the present study, we conducted comparative evaluation of the pathogenicity of viruses belonging to subgroups C2 and C3 (H15 and HN1 strains) in specific pathogen-free (SPF) chickens, and further compared them with previously determined pathogenicity of subgroup C4 (ES2 strain) virus. The HN1 strain showed lower viral replication in tissues, less transmissibility, and higher mean chicken lethal dose than the H15 and ES2 strains in SPF chickens. Considering that the HN1 strain has a different NS gene segment from the H15 and ES2 strains, the reassortment of the NS gene segment likely affects their infectivity and transmissibility in chickens. These findings emphasize the importance of monitoring the genetic characteristics and pathogenic features of HPAIVs to effectively control their outbreaks in the field.

Lumpy skin disease (LSD), caused by the LSD virus (LSDV), a dsDNA virus of the genus Capripoxvirus, represents a significant cross-border infectious threat, particularly impacting cattle and water buffaloes through transmission by blood-feeding insects. Traditionally endemic to Southern Africa, LSD has rapidly spread over the past decade through the Middle East to Eastern Europe and China, reaching Korea in October 2023. This outbreak prompted a nationwide vaccination campaign, addressing both the disease’s severe economic impact and its status as a notifiable disease under the World Organisation for Animal Health. This study assesses the seropositivity of the LSD vaccine in cattle across four Korean provinces 2–3 months post-vaccination, aiming to inform improvements in biosecurity and vaccination strategies. Overall, 30.59% of the cattle tested (1196 out of 3910) exhibited positive antibody responses, comparable to international post-vaccination findings. Analysis further revealed differences in the antibody positivity between farm types and management practices. Specifically, farms where vaccines were administered by veterinarians showed no significant difference in antibody positivity between Korean native cattle and dairy cattle, regardless of the presence of restraint facilities. However, on farms where vaccinations were conducted by the owners, dairy cattle demonstrated a higher seropositivity (43.30 ± 33.39%) compared to Korean native cattle (21.97 ± 20.79%) in the absence of restraint facilities. Further comparisons underscored the impact of restraint facilities on vaccination efficacy, with dairy farms generally achieving higher antibody positivity (29.43 ± 30.61%) than farms with Korean native cattle (23.02 ± 23.33%) (p < 0.05), suggesting that consistent vaccine delivery methods enhance immunogenic responses. Contrarily, no significant difference was noted in antibody positivity between large- and small-scale farms, indicating that farm size did not notably impact the effectiveness of the vaccinator. These findings emphasize that while current vaccines are sufficiently inducing immunity, enhancing vaccination strategies, particularly through trained personnel and improved restraint facilities, is crucial. This study’s insights into the impact of vaccination and farm management practices provide valuable guidance for refining LSD control measures in Korea and potentially other affected regions.

In this study, almost complete genomic sequences of PPV1 and PPV4 circulating in commercial pig farms in South Korea were obtained and analyzed. Important mutations that may be precursors to host changes, such as premature stop codons of PPV1 and frameshift mutations of PPV4, were observed in these sequences. A 27a-like strain of PPV1, known to show a lack of cross-neutralization against existing commercial vaccine strains, was identified by phylogenetic analysis. Given the active genetic evolution, the additional precursors to host changes and emerging new genotypes of PPVs need to be monitored through continuous sampling and genetic analysis.

Outbreaks caused by foot-and-mouth disease (FMD) A/ASIA/G-VII lineage viruses have often occurred in Middle Eastern and Southeast Asian countries since 2015. Because A/ASIA/G-VII lineage viruses are reported to have distinct antigenic relatedness with available commercial FMD vaccine strains, it is necessary to investigate whether inoculation with vaccines used in Korea could confer cross-protection against A/ASIA/G-VII lineage viruses. In the present study, we conducted two vaccination challenge trials to evaluate the efficacy of three commercial FMD vaccines (O/Manisa + O/3039 + A/Iraq, O/Campos + A/Cruzeiro + A/2001, and O/Primorsky + A/Zabaikalsky) against heterologous challenge with ASIA/G-VII lineage viruses (A/TUR/13/2017 or A/BHU/3/2017 strains) in pigs. In each trial, clinical signs, viremia, and salivary shedding of virus were measured for 7 days after challenge. In summary, the O/Campos + A/Cruzeiro + A/2001 vaccine provided full protection against two A/ASIA/G-VII lineage viruses in vaccinated pigs, where significant protection was observed. Although unprotected animals were observed in groups vaccinated with O/Manisa + O/3039 + A/Iraq or O/Primorsky + A/Zabaikalsky vaccines, the clinical scores and viral RNA levels in the sera and oral swabs of vaccinated animals were significantly lower than those of unvaccinated controls.

To analyze the relationship between homologous and heterologous serological titers of immunized pigs and their protection statuses against FMD virus challenges, in the present study, the correlation between the virus neutralization titers at 21 and 28 dpv and the protection statuses at 28 dpv against challenge with FMD virus was analyzed using data sets comprising five different combinations of homologous or heterologous challenge experiments in pigs vaccinated with type O (n = 96), A (n = 69), and Asia 1 (n = 74). As a result, the experiments were divided into three groups (21D-1, 21D-2, and 21D-3) in the 21-dpv model and two groups (28D-1 and 28D-2) in the 28-dpv model. Each response curve of groups 21D-1 and 21D-2 in the 21-dpv model was very similar to each curve of groups 28D-1 and 28D-2 in the 28-dpv model, respectively, even though there was an exceptional extra group (21D-3) in the 21-dpv model. The average titers estimating 0.75 probability of protection ranged from 1.06 to 1.62 log10 in the 21-dpv model and from 1.26 to 1.64 log10 in the 28-dpv model. In summary, we demonstrated that the serological method is useful for predicting the homologous and heterologous protection statuses of vaccinated pigs.

Novel swine orthopneumovirus (SOV) infections have been identified in pigs in the USA and some European countries but not in Asian countries, including South Korea, to date. The current study reports the first SOV infections in four domestic pig farms located in four provinces across South Korea. The detection rate of SOV in oral fluid samples using qRT-PCR was 4.4% (14/389), indicating the presence of the virus in pigs at commercial farms in Korea. Two complete genome sequences and one glycoprotein (G) gene sequence were obtained from SOV-positive samples. The complete genome analysis of KSOV-2201 and KSOV-2202 strains showed 98.2 and 95.4% homologies with a previously reported SOV, and the phylogenetic tree exhibited a high correlation with a previously reported SOV strain from the US and a canine pneumovirus (CPnV) strain from China. Based on the genetic analysis of the viral G gene, the murine pneumonia virus (MPV)-like orthopneumoviruses (MLOVs) were divided into two genogroups (G1 and G2). Seventeen CPnVs and two feline pneumoviruses were grouped into G1, while the Korean SOV strains identified in this study were grouped into G2 along with one SOV and two CPnVs. These results will contribute to expanding our understanding of the geographical distribution and genetic characteristics of the novel SOV in the global pig population.