Seoul Virus Infection and Spread in United States Home-Based Ratteries: Rat and Human Testing Results From a Multistate Outbreak Investigation.

BACKGROUND: During 2017, a multistate outbreak investigation occurred after the confirmation of Seoul virus (SEOV) infections in people and pet rats. A total of 147 humans and 897 rats were tested. METHODS: In addition to immunoglobulin (Ig)G and IgM serology and traditional reverse-transcription polymerase chain reaction (RT-PCR), novel quantitative RT-PCR primers/probe were developed, and whole genome sequencing was performed. RESULTS: Seventeen people had SEOV IgM, indicating recent infection; 7 reported symptoms and 3 were hospitalized. All patients recovered. Thirty-one facilities in 11 US states had SEOV infection, and among those with ≥10 rats tested, rat IgG prevalence ranged 2%-70% and SEOV RT-PCR positivity ranged 0%-70%. Human laboratory-confirmed cases were significantly associated with rat IgG positivity and RT-PCR positivity (P = .03 and P = .006, respectively). Genomic sequencing identified >99.5% homology between SEOV sequences in this outbreak, and these were >99% identical to SEOV associated with previous pet rat infections in England, the Netherlands, and France. Frequent trade of rats between home-based ratteries contributed to transmission of SEOV between facilities. CONCLUSIONS: Pet rat owners, breeders, and the healthcare and public health community should be aware and take steps to prevent SEOV transmission in pet rats and to humans. Biosecurity measures and diagnostic testing can prevent further infections.

Genetic analyses of Seoul hantavirus genome recovered from rats (Rattus norvegicus) in the Netherlands unveils diverse routes of spread into Europe.

Seoul virus (SEOV) is the etiologic agent of hemorrhagic fever with renal syndrome. It is carried by brown rats (Rattus norvegicus), a commensal rodent that closely cohabitates with humans in urban environments. SEOV has a worldwide distribution, and in Europe, it has been found in rats in UK, France, Sweden, and Belgium, and human cases of SEOV infection have been reported in Germany, UK, France, and Belgium. In the search of hantaviruses in brown rats from the Netherlands, we found both serological and genetic evidence for the presence of SEOV in the local wild rat population. To further decipher the relationship with other SEOV variants globally, the complete genome of SEOV in the Netherlands was recovered. SEOV sequences obtained from three positive rats (captured at close trapping locations at the same time) were found highly similar. Phylogenetic analyses demonstrated that two lineages of SEOV circulate in Europe. Strains from the Netherlands and UK, together with the Baxter strain from US, constitute one of these two, while the second includes strains from Europe and Asia. Our results support a hypothesis of diverse routes of SEOV spread into Europe. These findings, combined with other indications on the expansion of the spatial European range of SEOV, suggest an increased risk of this virus for the public health, highlighting the need for increased surveillance.

Autochthonous Human Case of Seoul Virus Infection, the Netherlands.

Orthohantaviruses are a group of rodentborne viruses with a worldwide distribution. The orthohantavirus Seoul virus (SEOV) can cause hemorrhagic fever with renal syndrome in humans and is distributed worldwide, like its reservoir host, the rat. Cases of SEOV in wild and pet rats have been described in several countries, and human cases have been reported in the United Kingdom, France, Canada, and the United States. In the Netherlands, SEOV has previously been found in wild brown rats. We describe an autochthonous human case of SEOV infection in the Netherlands. This patient had nonspecific clinical symptoms of an orthohantavirus infection (gastrointestinal symptoms and distinct elevation of liver enzymes). Subsequent source investigation revealed 2 potential sources, the patient's feeder rats and a feeder rat farm. At both sources, a high prevalence of SEOV was found in the rats. The virus closely resembled the Cherwell and Turckheim SEOV strains that were previously found in Europe.

Outbreak of Seoul Virus Among Rats and Rat Owners - United States and Canada, 2017.

In December 2016, the Wisconsin Department of Health Services (WDHS) notified CDC of a patient hospitalized with fever, leukopenia, elevated transaminases, and proteinuria. The patient owned and operated an in-home rattery, or rat-breeding facility, with approximately 100 Norway rats, primarily bred as pets. A family member developed similar symptoms 4 weeks later, but was not hospitalized. Because both patients were known to have rodent contact, they were tested for hantavirus infections. In January 2017, CDC confirmed recent, acute Seoul virus infection in both patients. An investigation was conducted to identify additional human and rat infections and prevent further transmission. Ultimately, the investigation identified 31 facilities in 11 states with human and/or rat Seoul virus infections; six facilities also reported exchanging rats with Canadian ratteries. Testing of serum samples from 183 persons in the United States and Canada identified 24 (13.1%) with Seoul virus antibodies; three (12.5%) were hospitalized and no deaths occurred. This investigation, including cases described in a previously published report from Tennessee (1), identified the first known transmission of Seoul virus from pet rats to humans in the United States and Canada. Pet rat owners should practice safe rodent handling to prevent Seoul virus infection (2).

Case report: two confirmed cases of human Seoul virus infections in Indonesia.

BACKGROUND: Seoul virus (SEOV) is a member of hantavirus family, which is transmitted to humans by Rattus rattus and Rattus norvegicus. Diagnosing SEOV infection is difficult because the clinical presentations are often undifferentiated with other viral or bacterial infections and assays to test antibodies seroconversion and RNA detection are not available in resource-limited setting like Indonesia. CASE PRESENTATION: We report two confirmed cases of SEOV infection from Indonesia. Here, we illustrate the clinical presentations, hematology and biochemistry profiles, and outcomes of the two cases. Phylogenetic analysis revealed that SEOV sequences have highest homology to isolates obtained from rodents in Indonesia. CONCLUSIONS: This report highlights the importance of considering SEOV infection in febrile patients with lymphopenia, thrombocytopenia, and elevation of liver enzyme despite the absence of hemorrhagic manifestations and renal syndromes. The public health importance of rodent-borne diseases such as SEOV infection urges an integrated epidemiological surveillance both in humans and rodents in Indonesia.

A seroprevalence study to determine the frequency of hantavirus infection in people exposed to wild and pet fancy rats in England.

Recent cases of acute kidney injury due to Seoul hantavirus infection from exposure to wild or pet fancy rats suggest this infection is increasing in prevalence in the UK. We conducted a seroprevalence study in England to estimate cumulative exposure in at-risk groups with contact with domesticated and wild rats to assess risk and inform public health advice. From October 2013 to June 2014, 844 individual blood samples were collected. Hantavirus seroprevalence amongst the pet fancy rat owner group was 34.1% (95% CI 23·9-45·7%) compared with 3·3% (95% CI 1·6-6·0) in a baseline control group, 2·4% in those with occupational exposure to pet fancy rats (95% CI 0·6-5·9) and 1·7% with occupational exposure to wild rats (95% CI 0·2-5·9). Variation in seroprevalence across groups with different exposure suggests that occupational exposure to pet and wild rats carries a very low risk, if any. However incidence of hantavirus infection among pet fancy rat owners/breeders, whether asymptomatic, undiagnosed mild viral illness or more severe disease may be very common and public health advice needs to be targeted to this at-risk group.

Influence of HLA-DRB alleles on haemorrhagic fever with renal syndrome in a Chinese Han population in Hubei Province, China.

Specific human leucocyte antigen (HLA) alleles are considered a genetic risk factor for the progression of haemorrhagic fever with renal syndrome (HFRS) caused by hantaviruses. The aim of this study was to establish whether HLA-DRB alleles are associated with the severity of HFRS caused by different types of hantaviruses in a Chinese Han population from Hubei Province of central China. Twenty-two specific HLA-DRB alleles were analysed by sequence-specific primer-polymerase chain reaction (SSP-PCR) in 100 HFRS patients and 213 healthy volunteers. Associations of HLA-DRB alleles with the severity and clinical parameters of HFRS caused by Hantaan virus (HTNV) or Seoul virus (SEOV) infection were evaluated. Six alleles (HLA-DRB1*0401-0411, HLA-DRB1*1001, HLA-DRB1*1101-1105, HLA-DRB1*1201-1202, HLA-DRB1*1305 and DRB5*0101-0201) demonstrated strong associations with HFRS caused by HTNV and SEOV infections. Further comparison of these HLA-DRB1 allele frequencies between HFRS patients with differing severities and healthy controls demonstrated that the HLA-DRB1*0401-0411, HLA-DRB1*1001 and DRB1*1305 alleles were more frequent in the moderate course of HTNV-infected HFRS. Meanwhile, the DRB1*1101-1105 allele was more frequently observed in the severe course of HTNV-infected HFRS. We also found that the HLA-DRB1*1201-1202 allele frequency was higher in the moderate course of SEOV-infected HFRS, whereas the DRB5*0101-0201 allele may play a protective role in moderate HFRS caused by both HTNV and SEOV infections. These results provide evidence of the influence of HLA-DRB on the severity of HFRS and confirm the effect of HLA-DRB on HFRS during different types of hantavirus infection in a Chinese Han population in Hubei Province, China.

Molecular and serological evidence for Seoul virus in rats (Rattus norvegicus) in Zhangmu, Tibet, China.

We report the detection of a virus, tentatively identified as Seoul virus (SEOV), from a rat (Rattus norvegicus) collected in the city of Zhangmu, Tibet. SEOV RNA was detected in lung tissue by reverse transcription (RT)-PCR, followed by sequencing. Serum samples collected from Zhangmu were positive for SEOV-specific antibodies (indirect fluorescent antibody test that used SEO antigen). Sequencing and phylogenetic analysis of partial L and S sequences together with serology results suggest that the Zhangmu01 hantavirus is an isolate of SEOV, that hantaviruses circulate in Tibet, and that rats may act as natural reservoirs for the virus.

Detection and genetic characterization of Seoul virus from commensal brown rats in France.

BACKGROUND: Hantaviruses are single-stranded RNA viruses, which are transmitted to humans primarily via inhalation of aerosolised virus in contaminated rodent urine and faeces. Whilst infected reservoir hosts are asymptomatic, human infections can lead to two clinical manifestations, haemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS), with varying degrees of clinical severity. The incidence of rodent and human cases of Seoul virus (SEOV) in Europe has been considered to be low, and speculated to be driven by the sporadic introduction of infected brown rats (Rattus norvegicus) via ports. METHODS: Between October 2010 and March 2012, 128 brown rats were caught at sites across the Lyon region in France. RESULTS: SEOV RNA was detected in the lungs of 14% (95% CI 8.01-20.11) of brown rats tested using a nested pan-hantavirus RT-PCR (polymerase gene). Phylogenetic analysis supports the inclusion of the Lyon SEOV within Lineage 7 with SEOV strains originating from SE Asia and the previously reported French & Belgian SEOV strains. Sequence data obtained from the recent human SEOV case (Replonges) was most similar to that obtained from one brown rat trapped in a public park in Lyon city centre. We obtained significantly improved recovery of virus genome sequence directly from SEOV infected lung material using a simple viral enrichment approach and NGS technology. CONCLUSIONS: The detection of SEOV in two wild caught brown rats in the UK and the multiple detection of SEOV infected brown rats in the Lyon region of France, suggests that SEOV is circulating in European brown rats. Under-reporting and difficulties in identifying the hantaviruses associated with HFRS may mask the public health impact of SEOV in Europe.

Rats (Rattus norvegicus and Rattus losea) harboring Seoul hantavirus in Qingyuan, southern China: a survey during 2011-2013.

Hemorrhagic fever with renal syndrome (HFRS) is a zoonotic disease, which threatens public health and its incidence has increased sharply up to the present time in southern China. A survey of HFRS including in both the natural hosts and humans conducted in Qingyuan, southern China, during 2011-2013 revealed that one, two and seven confirmed cases of HFRS occurred in 2011, 2012 and 2013, respectively. Rodent densities ranged 1.73%-12.2% and Seoul hantavirus was detected by RT-PCR only in Rattus norvegicus and Rattus losea. The positive rate in humans was 0.95% serologically and 0.94% with IIFA in 2011 and 2013, respectively. DNA fragments detected in Rattus norvegicus and Rattus losea were highly homologous with those of Seoul hantavirus HB55 (96.2%) and L99 (95.1%), respectively. Thus HFRS is becoming an emerging and dangerous disease in southern China and it is necessary to further perform molecular characterization of strains isolated from rodents and humans.

The discovery of novel variants reveals the genetic diversity and potential origin of Seoul orthohantavirus.

Seoul orthohantavirus (SEOV) has been identified as one of the main causative agents of hemorrhagic fever with renal syndrome (HFRS) in China. The virus was found circulating in rodent populations in almost all provinces of the country, reflecting the wide distribution of HFRS. Here, using the direct immunofluorescence assay (DFA) and real-time quantitative reverse transcription PCR (qRT-PCR) approach, we performed screening in 1784 small mammals belonging to 14 species of three orders captured in the main areas of HFRS endemicity in Yunnan province (southwestern China) and identified 37 SEOV-positive rats (36 Rattus norvegicus and 1 Rattus tanezumi). A 3-year surveillance of HFRS epidemics and dynamics of rodent reservoir density and virus prevalence implied a potential correlation between them. The subsequent meta-transcriptomic sequencing and phylogenetic analyses revealed three SEOV variants, among which two are completely novel. The ancestral character state reconstruction (ACSR) analysis based on both novel variants and documented strains from 5 continents demonstrated that SEOV appeared to originate near the southwestern area (Yunnan-Kweichow Plateau) of China, then could spread to other regions and countries by their rodent carriers, resulting in a global distribution today. In summary, these data furthered the understanding regards genetic diversity and the potential origin for SEOV. However, the expanding endemic foci in the province suggest that the virus is spreading over a wider region and is much more diverse than previous depicted, which means that increased sampling is necessary.

Distribution and genetic characterization of hantaviruses in bats and rodents from Yunnan.

Hemorrhagic fever with renal syndrome caused by hantaviruses has long been a serious public health issue in Yunnan Province. Hantaviruses exhibit a high extent of biodiversity in their natural hosts, particularly in mammalian hosts. This study was conducted to screen for hantaviruses in bats and rodents in Yunnan Province and elucidate their genetic characteristics and possible zoonotic disease risk. Hantaviruses were detected in 202 bats and 372 rodents with the positive rates 27.49% and 1.25% respectively. A novel lineage (named Lineage 10) of the Seoul virus (SEOV) from rodents and the geographic clustering of hantavirus in bats were identified using phylogenetic analyses of the full-length M- and S-segments. Our study suggest a high cross-species transmissibility of hantaviruses in bats and existence of a new lineage of SEOV in rodents differing significantly from other SEOVs. These results provide data to support the prevention and control of hantavirus-associated diseases in Yunnan Province.

Evolution and genetic characterization of Seoul virus in wild rats Rattus norvegicus from an urban park in Lyon, France 2020-2022.

BACKGROUND: Seoul virus (SEOV) is an orthohantavirus primarily carried by rats. In humans, it may cause hemorrhagic fever with renal syndrome (HFRS). Its incidence is likely underestimated and given the expansion of urban areas, a better knowledge of SEOV circulation in rat populations is called for. Beyond the need to improve human case detection, we need to deepen our comprehension of the ecological, epidemiological, and evolutionary processes involved in the transmission of SEOV. METHODOLOGY / PRINCIPAL FINDINGS: We performed a comprehensive serological and molecular characterization of SEOV in Rattus norvegicus in a popular urban park within a large city (Lyon, France) to provide essential information to design surveillance strategies regarding SEOV. We sampled rats within the urban park of 'La Tête d'Or' in Lyon city from 2020 to 2022. We combined rat population genetics, immunofluorescence assays, SEOV high-throughput sequencing (S, M, and L segments), and phylogenetic analyses. We found low structuring of wild rat populations within Lyon city. Only one sampling site within the park (building created in 2021) showed high genetic differentiation and deserves further attention. We confirmed the circulation of SEOV in rats from the park with high seroprevalence (17.2%) and high genetic similarity with the strain previously described in 2011 in Lyon city. CONCLUSION/SIGNIFICANCE: This study confirms the continuous circulation of SEOV in a popular urban park where the risk for SEOV transmission to humans is present. Implementing a surveillance of this virus could provide an efficient early warning system and help prepare risk-based interventions. As we reveal high gene flow between rat populations from the park and the rest of the city, we advocate for SEOV surveillance to be conducted at the scale of the entire city.

Migration of Norway rats resulted in the worldwide distribution of Seoul hantavirus today.

Despite the worldwide distribution, most of the known Seoul viruses (SEOV) are closely related to each other. In this study, the M and the S segment sequences of SEOV were recovered from 130 lung tissue samples (mostly of Norway rats) and from six patient serum samples by reverse transcription-PCR. Genetic analysis revealed that all sequences belong to SEOV and represent 136 novel strains. Phylogenetic analysis of all available M and S segment sequences of SEOV, including 136 novel Chinese strains, revealed four distinct groups. All non-Chinese SEOV strains and most of the Chinese variants fell into the phylogroup A, while the Chinese strains originating from mountainous areas clustered into three other distinct groups (B, C, and D). We estimated that phylogroup A viruses may have arisen only within the last several centuries. All non-Chinese variants appeared to be directly originated from China. Thus, phylogroup A viruses distributed worldwide may share a recent ancestor, whereas SEOV seems to be as diversified genetically as other hantaviruses. In addition, all available mitochondrial DNA (mtDNA) sequences of Norway rats, including our 44 newly recovered mtDNA sequences, were divided into two phylogenetic groups. The first group, which is associated with the group A SEOV variants, included most of rats from China and also all non-Chinese rats, while the second group consisted of a few rats originating only from mountain areas in China. We hypothesize that an ancestor of phylogroup A SEOV variants was first exported from China to Europe and then spread through the New World following the migration of Norway rats.

A two-tube multiplex real-time RT-PCR assay for the detection of four hemorrhagic fever viruses: severe fever with thrombocytopenia syndrome virus, Hantaan virus, Seoul virus, and dengue virus.

The aim of this study was to develop and evaluate a two-tube multiplex real-time RT-PCR assay for the detection and identification of four viral hemorrhagic fever (VHF) pathogens, severe fever with thrombocytopenia syndrome virus (SFTSV), Hantaan virus (HTNV), Seoul virus (SEOV), and dengue virus (DENV), from human clinical samples. The two-tube multiplex real-time RT-PCR assay we developed has a sensitivity of 10 copies/µL for each of the targets, and the performance was linear within the range of at least 10(7) transcript copies. Moreover, we evaluated the specificity of the assay using other virus RNA as template, and found no cross-reactivity. This new assay is able to detect SFTSV, HTNV, SEOV and DENV in two reactions and brings a cost of 40 % compared to separate reactions. Evaluation of this assay with clinical serum samples from laboratory-confirmed patients and healthy donors showed 100 % clinical diagnostic sensitivity and over 99 % specificity. The assay was applied for scanning 346 clinical samples collected from patients admitted to the hospital with suspected VHF and compared with virus isolation and immunofluorescence assay (IFA). The assay indentified 59 SFTSV-, 12 HTNV-, 11 SEOV- and 9 DENV-positive samples and showed higher sensitivity. This assay thus provides a reliable and cost-effective screening tool for early clinical diagnosis of SFTSV, HTNV, SEOV and DENV in the acute phase.

A survey of rodent-borne pathogens carried by wild Rattus spp. in Northern Vietnam.

To examine the prevalence of human pathogens carried by rats in urban areas in Hanoi and Hai Phong, Vietnam, we live-trapped 100 rats in January 2011 and screened them for a panel of bacteria and viruses. Antibodies against Leptospira interrogans (22·0%), Seoul virus (14·0%) and rat hepatitis E virus (23·0%) were detected in rats, but antibodies against Yersinia pestis were not detected. Antibodies against L. interrogans and Seoul virus were found only in adult rats. In contrast, antibodies to rat hepatitis E virus were also found in juvenile and sub-adult rats, indicating that the transmission mode of rat hepatitis E virus is different from that of L. interrogans and Seoul virus. Moreover, phylogenetic analyses of the S and M segments of Seoul viruses found in Rattus norvegicus showed that Seoul viruses from Hai Phong and Hanoi formed different clades. Human exposure to these pathogens has become a significant public health concern.

The continued emergence of hantaviruses: isolation of a Seoul virus implicated in human disease, United Kingdom, October 2012.

Following a suspected case of hantavirus in a patientsuffering from acute kidney injury, rodents fromthe patient's property in Yorkshire and the Humber,United Kingdom (UK) were screened for hantaviruses.Hantavirus RNA was detected via RT-PCR in two Rattusnorvegicus. Complete sequencing and phylogeneticanalysis established the virus as a Seoul hantavirus,which we have provisionally designated as strainHumber. This is the first hantavirus isolated from wildrodents in the UK and confirms the presence of a pathogenicSeoul virus in Europe.

Severe pulmonary involvement in a case attributed to domestically acquired Seoul hantavirus in the United States.

Hantavirus is known to cause 2 distinct clinical syndromes: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome. Seoul virus is an Old World hantavirus known to cause HFRS. We report a case attributed to domestically acquired Seoul hantavirus with prominent pulmonary involvement and a fatal outcome.

Pathogenicity of a natural reassortant hantavirus CGRn9415 in newborn rats and newborn mice.

To better understand the pathogenicity and infectivity of a natural reassortant CGRn9415 generated from Hantaan virus (HTNV) and Seoul virus (SEOV), CGRn9415, HTNV 76-118 and SEOV L99 were used to infect newborn Kunming (KM) mice and newborn Wistar rats. In KM mice, there was no statistical difference between the death rate with CGRn9415 and that of L99, while 76-118 killed all mice even at low dosage; CGRn9415 killed all infected rats similar to L99 at the dosage of 10(5) f.f.u., while no death occurred in rats infected with 76-118 even as high as 2 × 10(5) f.f.u., suggesting that the reassortant CGRn9415 possesses similar pathogenicity as L99. Furthermore, the reassortant CGRn9415 could establish a persistent infection in both KM mice and Wistar rats more easily than 76-118 or L99. These data suggest that the reassorted hantavirus behaves more like SEOV as far as the pathogenicity is concerned.

Genetic characterization of seoul hantavirus originated from norway rats (Rattus norvegicus) captured in Belgium.

Hantaviruses (genus Hantavirus, family Bunyaviridae) cause hemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus (cardio)pulmonary syndrome (HCPS) in the Americas. So far, in Europe, four pathogenic hantaviruses have been found, often in co-circulation: Puumala virus (PUUV), Dobrava virus (DOBV), Saaremaa virus (SAAV), and Seoul virus (SEOV). Of those, only PUUV was found in Belgium. Recently, in our search for hantaviruses in the Flanders region of Belgium we collected genetic and serological evidence for the presence of SEOV virus in local brown rats. In this article, the results of (phylo)genetic analysis of wild-type SEOV strain from the Flanders are presented. The analysis based on the complete S segment sequence and also partial M- and L-segment sequences revealed that the Belgian SEOV strain was related most closely to strains from France, Indonesia, Japan, Singapore, Cambodia (those associated with the species Rattus norvegicus) and Vietnam. Such a clustering was in perfect agreement with the results of direct sequence comparison and suggested the same evolutionary history for all three genome segments of the Belgian SEOV strain (i.e., no reassortment of genome segments). So far, SEOV has been found in two European countries, France and Belgium, and there is every reason to believe that the area of the virus distribution in Europe is not restricted to those countries.