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A nationwide survey of chigger mites causing scrub typhus and an investigation of epidemiologic factors for chigger mites was conducted at 16 localities in 8 provinces in Korea during autumn 2009, 2012, and 2013. A total of 233 Apodemus agrarius were captured, and all were infested with chigger mites. The chigger index was highest in Chungcheongbuk-do in 2009 (358.3) and 2012 (290.1) and Chungcheongnam-do in 2013 (294.4). The predominant chigger mite species was Leptotrombidium pallidum in the northern and central parts and L. scutellare in the southern and western parts, Korea. L. pallidum was not found in Jellanam-do and Gyeongsangnam-do and the distribution of L. scutellare had been expanded in the northern parts of Korea. The chigger index of L. pallidum was positively correlated with temperature and negatively correlated with humidity. The incidence of scrub typhus is dependent on L. scutellare index. These findings could be helpful to monitor the distribution of chigger mites and to develop a preventive measures for scrub typhus in Korea.

Paramyxoviruses harbored by multiple natural reservoirs pose a potential threat to public health. Jeilongvirus has been proposed as a novel paramyxovirus genus found in rodents, bats, and cats. Paramyxovirus RNA was detected in 108/824 (13.1%) Apodemus agrarius captured at 14 trapping sites in the Republic of Korea. We first present two genetically distinct novel paramyxoviruses, Paju Apodemus paramyxovirus 1 (PAPV-1) and 2 (PAPV-2). The disparity between PAPV-1 (19,716 nucleotides) and -2 (17,475 nucleotides) revealed the presence of the SH gene and length of the G gene in the genome organization. The phylogeny of PAPV-1 and -2 belonged to distinct genetic lineages of Jeilongvirus, respectively, even though these viruses were originated from A. agrarius. PAPV-1 infected human epithelial and endothelial cells, facilitating the induction of type I/III interferons, interferon-stimulated genes, and pro-inflammatory cytokines. Therefore, this study provides insights into the molecular epidemiology, genetic diversity, and virus-host interactions of novel rodent-borne paramyxoviruses.

Two-point mutations (V419L and L925I) on the voltage-sensitive sodium channel of bed bugs (Cimex lectularius) are known to confer pyrethroid resistance. To determine the status of pyrethroid resistance in bed bugs in Korea, resistance allele frequencies of bed bug strains collected from several US military installations in Korea and Mokpo, Jeollanamdo, from 2009-2019 were monitored using a quantitative sequencing. Most bed bugs were determined to have both of the point mutations except a few specimens, collected in 2009, 2012 and 2014, having only a single point mutation (L925I). No susceptible allele was observed in any of the bed bugs examined, suggesting that pyrethroid resistance in bed bug populations in Korea has reached a serious level. Large scale monitoring is required to increase our knowledge on the distribution and prevalence of pyrethroid resistance in bed bug populations in Korea. Based on present study, it is urgent to restrict the use of pyrethroids and to introduce effective alternative insecticides. A nation-wide monitoring program to determine the pyrethroid resistance level in bed bugs and to select alternative insecticides should be implemented.

Paramyxoviruses, negative-sense single-stranded RNA viruses, pose a critical threat to human public health. Currently, 78 species, 17 genera, and 4 subfamilies of paramyxoviruses are harbored by multiple natural reservoirs, including rodents, bats, birds, reptiles, and fish. Henipaviruses are critical zoonotic pathogens that cause severe acute respiratory distress and neurological diseases in humans. Using reverse transcription-polymerase chain reaction, 115 Crocidura species individuals were examined for the prevalence of paramyxovirus infections. Paramyxovirus RNA was observed in 26 (22.6%) shrews collected at five trapping sites, Republic of Korea. Herein, we report two genetically distinct novel paramyxoviruses (genus: Henipavirus): Gamak virus (GAKV) and Daeryong virus (DARV) isolated from C. lasiura and C. shantungensis, respectively. Two GAKVs and one DARV were nearly completely sequenced using next-generation sequencing. GAKV and DARV contain six genes (3′-N-P-M-F-G-L-5′) with genome sizes of 18,460 nucleotides and 19,471 nucleotides, respectively. The phylogenetic inference demonstrated that GAKV and DARV form independent genetic lineages of Henipavirus in Crocidura species. GAKV-infected human lung epithelial cells elicited the induction of type I/III interferons, interferon-stimulated genes, and proinflammatory cytokines. In conclusion, this study contributes further understandings of the molecular prevalence, genetic characteristics and diversity, and zoonotic potential of novel paramyxoviruses in shrews.

There are eight Anopheles spp. present in the Republic of Korea (ROK), including five members of the Anopheles Hyrcanus Group that cannot be identified using current morphological methods. The vector competence of only Anopheles sinensis s.s., An. lesteri, and An. kleini have been investigated. As the geographical distribution of Anopheles spp. varies in the ROK, determining the relative vector competence of the Anopheles spp. provides a basis for delineating malaria risks to Korean populations and U.S. military/civilian populations deployed to the ROK. Anopheles belenrae and An. pullus, collected from a malaria high-risk area in the ROK, were evaluated for vector competence of P. vivax. A total of 1,000 each of An. dirus (Thai strain), and Korean strains of An. pullus and An. belenrae were fed on P. vivax infected blood collected from Thai patients via artificial membrane feeding. The overall oocyst infection rates for An. dirus, An. pullus, and An. belenrae dissected on days 8–9 postfeed were 64.1, 12.0, and 11.6%, respectively. The overall sporozoite infection rates for those species dissected on days 14–15 postfeed were 84.5, 3.4, and 5.1% respectively. The salivary gland sporozoite indices for positive females with +4 (>1,000 sporozoites) were observed in An. dirus (72.8%), but not observed for either An. pullus or An. belenrae. Most sporozoite-positive An. pullus (83.3%) and An. belenrae (71.4%) females were observed with only +1 (1–10 sporozoites) salivary glands. These data indicate that both An. belenrae and An. pullus are very poor vectors of P. vivax.

Tick-borne pathogens are contributing factors for the increased incidence of vector-borne diseases throughout the world, including Lyme borreliosis, one of the most prevalent spirochetes belonging to the Borrelia burgdorferi sensu lato group. The present study focused on the detection of Borrelia species from hard ticks collected at U.S. Army Garrison Humphreys, Republic of Korea (ROK), using molecular and genotypic analyses. Tick-borne disease surveillance was conducted from January to December, 2018–2019. A total of 24,281 ticks (2 genera and 5 species) were collected from road-killed Korean Water deer (KWD) and by tick drag. Haemaphysalis longicornis (92.0%) was the most commonly collected species, followed by Haemaphysalis flava (4.9%), Ixodes nipponensis (3.1%), Haemaphysalis phasiana (0.07%), and Haemaphysalis japonica (

When free-ranging birds are accidentally killed or die, there may be greater potential for their associated ticks to detach, seek alternate hosts, and become established. We examined 711 carcasses of 95 avian species for ticks at a stopover island of migratory birds in the Republic of Korea where only Ixodes nipponensis and I. persulcatus were previously reported from local mammals and vegetation. A total of 16 ticks, I. turdus and Haemaphysalis flava, were collected from 8 fresh carcasses belonging to 5 avian species. Despite their known abundance on migratory birds and mainland Korea, these species had not colonized the isolated insular ecosystem possibly due to the low abundance and diversity of local hosts. The results imply that increasing human impact, such as the anthropogenic mortality of migratory birds and the introduction of non-native mammalian hosts, will increase the potential invasion and colonization risk of ticks. This finding also suggests that tick surveillance consisting of fresh carcasses of dead migratory birds may provide additional information, often ignored in surveillance of ticks on live birds, for the potential introduction of non-native ticks and associated pathogens affecting animal and human health.

Background Genus Anopheles mosquitoes are the primary vectors of human malaria, which is a serious threat to public health worldwide. To reduce the spread of malaria and identify the malaria infection rates in mosquitoes, accurate species identification is needed. Malaria re-emerged in 1993 in the Republic of Korea (ROK), with numbers peaking in 2004 before decreasing to current levels. Eight Anopheles species (Anopheles sinensis, Anopheles pullus, Anopheles belenrae, Anopheles lesteri, Anopheles kleini, Anopheles sineroides, Anopheles koreicus, Anopheles lindesayi) are distributed throughout Korea. Members of the Anopheles Hyrcanus group currently cannot be identified morphologically. The other species of Anopheles can be identified morphologically, except when specimens are damaged in traps. The purpose of this study was to develop a rapid and accurate method for simultaneous molecular identification of the eight Anopheles species present in the ROK. Methods Anopheles spp. used in this study were collected near/in the demilitarized zone in ROK, where most malaria cases are reported. DNA from 165 of the Anopheles specimens was used to develop a multiplex PCR assay. The internal transcribed spacer 2 (ITS2) region of each species was sequenced and analysed for molecular identification. Results DNA from a total of 165 Anopheles specimens was identified to species using a multiplex diagnostic system. These included: 20 An. sinensis, 21 An. koreicus, 17 An. lindesayi, 25 An. kleini, 11 An. lesteri, 22 An. sineroides, 23 An. belenrae, and 26 An. pullus. Each species was clearly distinguished by electrophoresis as follows: 1,112 bp for An. sinensis; 925 bp for An. koreicus; 650 bp for An. lindesayi; 527 bp for An. kleini; 436 bp for An. lesteri; 315 bp for An. sineroides; 260 bp for An. belenrae; and, 157 bp for An. pullus. Conclusion A multiplex PCR assay was developed to identify Anopheles spp. distributed in ROK. This method can be used to accurately identify Anopheles species that are difficult to identify morphologically to determine species distributions and malaria infection rates.

Whole-genome sequencing of infectious agents enables the identification and characterization of emerging viruses. The MinION device is a portable sequencer that allows real-time sequencing in fields or hospitals. Hantaan orthohantavirus (Hantaan virus, HTNV), harbored by Apodemus agrarius, causes hemorrhagic fever with renal syndrome (HFRS) and poses a critical public health threat worldwide. In this study, we aimed to evaluate the feasibility of using nanopore sequencing for whole-genome sequencing of HTNV from samples having different viral copy numbers. Amplicon-based next-generation sequencing was performed in A. agrarius lung tissues collected from the Republic of Korea. Genomic sequences of HTNV were analyzed based on the viral RNA copy numbers. Amplicon-based nanopore sequencing provided nearly full-length genomic sequences of HTNV and showed sufficient read depth for phylogenetic analysis after 8 h of sequencing. The average identity of the HTNV genome sequences for the nanopore sequencer compared to those of generated from Illumina MiSeq revealed 99.8% (L and M segments) and 99.7% (S segment) identities, respectively. This study highlights the potential of the portable nanopore sequencer for rapid generation of accurate genomic sequences of HTNV for quicker decision making in point-of-care testing of HFRS patients during a hantavirus outbreak.

Ticks are important vectors of various pathogens that result in clinical illnesses in humans and domestic and wild animals. Information regarding tick infestations and pathogens transmitted by ticks is important for the identification and prevention of disease. This study was a large-scale investigation of ticks collected from dogs and their associated environments in the Republic of Korea (ROK). It included detecting six prevalent tick-borne pathogens (Anaplasma spp., A. platys, Borrelia spp., Babesia gibsoni, Ehrlichia canis, and E. chaffeensis). A total of 2293 ticks (1110 pools) were collected. Haemaphysalis longicornis (98.60%) was the most frequently collected tick species, followed by Ixodes nipponensis (0.96%) and H. flava (0.44%). Anaplasma spp. (24/1110 tick pools, 2.16%) and Borrelia spp. (4/1110 tick pools, 0.36%) were detected. The phylogenetic analyses using 16S rRNA genes revealed that the Anaplasma spp. detected in this study were closely associated with A. phagocytophilum reported in humans and rodents in the ROK. Borrelia spp. showed phylogenetic relationships with B. theileri and B. miyamotoi in ticks and humans in Mali and Russia. These results demonstrate the importance of tick-borne disease surveillance and control in dogs in the ROK.

This study was done to characterize distribution of Rickettsia spp. in ticks in the northwestern and southwestern provinces in the Republic of Korea. A total of 2,814 ticks were collected between May and September 2009. After pooling, 284 tick DNA samples were screened for a gene of Rickettsia-specific 17-kDa protein using nested PCR (nPCR), and produced 88 nPCR positive samples. Of these positives, 75% contained 190-kDa outer membrane protein gene (ompA), 50% 120-kDa outer membrane protein gene (ompB), and 64.7% gene D (sca4). The nPCR products of ompA, ompB, and sca4 genes revealed close relatedness to Rickettsia japonica, R. heilongjiangensis, and R. monacensis. Most Rickettsia species were detected in Haemaphysalis longicornis. This tick was found a dominant vector of rickettsiae in the study regions in the Republic of Korea.

Background Endemic outbreaks of hantaviruses pose a critical public health threat worldwide. Hantaan orthohantavirus (HTNV) causes hemorrhagic fever with renal syndrome (HFRS) in humans. Using comparative genomic analyses of partial and nearly complete sequences of HTNV from humans and rodents, we were able to localize, with limitations, the putative infection locations for HFRS patients. Partial sequences might not reflect precise phylogenetic positions over the whole-genome sequences; finer granularity of rodent sampling reflects more precisely the circulation of strains. Methods Five HFRS specimens were collected. Epidemiological surveys were conducted with the patients during hospitalization. We conducted active surveillance at suspected HFRS outbreak areas. We performed multiplex polymerase chain reaction–based next-generation sequencing to obtain the genomic sequence of HTNV from patients and rodents. The phylogeny of human- and rodent-derived HTNV was generated using the maximum likelihood method. For phylogeographic analyses, the tracing of HTNV genomes from HFRS patients was defined on the bases of epidemiological interviews, phylogenetic patterns of the viruses, and geographic locations of HTNV-positive rodents. Results The phylogeographic analyses demonstrated genetic clusters of HTNV strains from clinical specimens, with HTNV circulating in rodents at suspected sites of patient infections. Conclusions This study demonstrates a major shift in molecular epidemiological surveillance of HTNV. Active targeted surveillance was performed at sites of suspected infections, allowing the high-resolution phylogeographic analysis to reveal the site of emergence of HTNV. We posit that this novel approach will make it possible to identify infectious sources, perform disease risk assessment, and implement preparedness against vector-borne viruses.

The Anopheles Hyrcanus Group in the Republic of Korea (ROK) consists of 5 morphologically indistinct species that can only be identified with certainty by polymerase chain reaction (PCR). A total of 86 bloodfed Anopheles spp. were collected from a cow barn located in the village of Tongilchon near the demilitarized zone in the ROK on June 13, 2016, and sent to the Armed Forces Research Institute of Medical Sciences in Bangkok, Thailand, where they were identified to species by PCR. The 1st shipment contained 15 An. belenrae and 37 An. pullus females that were used to start the colonies. Parent females that oviposited were identified by PCR for colonization. A higher proportion of F1–F4 females of An. belenrae than An. pullus bloodfed when provided both blood meals on human arms and using a membrane feeding system with human blood. Following blood meals, the females were forced mated for colony maintenance. The mean numbers of eggs oviposited per female for An. belenrae was 127.7 ± 19.3 and for An. pullus was 136 ± 23.6. On average, at 25°C (±2°C) An. belenrae and An. pullus took 15.1 and 16.1 days to develop from egg to adult, respectively. A 2nd group of bloodfed Anopheles spp. was collected at the same location in the ROK on June 24, 2017. This group contained 13 An. belenrae and 27 An. pullus. Similarly, eggs were obtained and adults identified by PCR and then reared to adults and subsequent generations forced mated to members of each of the existing colonies to increase genetic diversity. The colonies were established to evaluate their susceptibility to vector vivax malaria, which is essential to better understand the epidemiology of malaria transmission in Korea. This is the 1st report of colonization of both An. belenrae and An. pullus.

Recent outbreaks of emerging and re-emerging viruses such as Zika, West Nile and Japanese encephalitis (JEV) viruses have shown that timely detection of novel arboviruses with epidemic potential is essential to mitigate human health risks. There have been rising concerns that an emergent JEV genotype (genotype V, GV) is circulating in Asia, against which the current US-FDA-approved JEV vaccine may not be efficacious. To ascertain if JEV GV and other arboviruses are circulating in East Asia, we conducted next-generation sequencing on 260 pools of Culex tritaeniorhynchus and Culex bitaeniorhynchus mosquitoes (6,540 specimens) collected at Camp Humphreys, Republic of Korea (ROK), from mid-May - October 2018. Metagenomic analysis demonstrated a highly abundant and diverse virome with correlates of health and ecological relevance. Additionally, two complete JEV GV genome sequences were obtained from separate mosquito pools, indicating that JEV GV is circulating in the Pyeongtaek area near Seoul, ROK. Retrospective sample and sequence analyses showed that JEV GV was also present in 2016 mosquito pools collected in Seoul, ROK. Sequence-based analysis of JEV GV indicates a divergent genotype that is the most distant from the GIII derived live attenuated SA14-14-2 vaccine strain. A GV E protein investigation and 3D modeling in context to SA14-14-2 indicated likely regions responsible for reduced antibody affinity, including clusters of significant amino acid changes at externally exposed domains. These data highlight the critical need for continued mosquito surveillance as a means of detecting and identifying emerging and re-emerging arboviruses of public health relevance. Importantly, our results emphasize recent concerns that there may be a possible shift in the circulating JEV genotype in East Asia and highlights the critical need for a vaccine proven to be efficacious against this re-emergent virus.

Biting midges (Culicoides: Ceratopogonidae) were collected using New Jersey light traps at Yongsan US Army Garrison (USAG;urban), Seoul Metropolitan city and Camp Humphreys USAG (rural), Pyeongtaek, Gyeonggi-do (province), Republic of Korea , from May-October 2010-2013 and 2015-2017, to determine species composition and seasonal distribution patterns in urban and rural habitats. A total of 9,958 female (53.85%) and 8,533 male (46.15%) Culicoides comprising 16 species were collected. Overall, the most commonly collected species was Culicoides arakawae (74.3%), followed by C. circumscriptus (16.2%), C. kibunensis (2.5%), C. nasuensis (2.2%), C. clavipalpis (1.4%), and C. pallidulus (1.3%), while the remaining 10 species accounted for

Background Genus Anopheles mosquitoes are the primary vectors of human malaria, which is a serious threat to public health worldwide. To reduce the spread of malaria and identify the malaria infection rates in mosquitoes, accurate species identification is needed. Malaria reemerged in 1993 in the Republic of Korea (ROK), with numbers peaking in 2004 before decreasing to current levels. Eight Anopheles species (Anopheles sinensis, An. pullus, An. belenrae, An. lesteri, An. kleini, An. sineroides, An. koreicus, and An. lindesayi) are distributed throughout Korea. Members of the Anopheles Hyrcanus Group currently cannot be identified morphologically. The other species of Anopheles can be identified morphologically, except when specimens are damaged in traps. The purpose of this study was to develop a rapid and accurate method for simultaneous molecular identification of the eight Anopheles species present in the ROK. Methods Anopheles spp. used in this study were collected near/in the demilitarized zone in the ROK, where most malaria cases are reported. DNA from 165 of the Anopheles specimens was used to develop a multiplex PCR assay. The internal transcribed spacer 2 (ITS2) region of each species was sequenced and analyzed for molecular identification. Results DNA from a total of 165 Anopheles specimens was identified to species using a multiplex diagnostic system. These included: 20 An. sinensis, 21 An. koreicus, 17 An. lindesayi, 25 An. kleini, 11 An. lesteri, 22 An. sineroides, 23 An. belenrae, and 26 An. pullus. Molecular weights determined by electrophoresis were 1112 bp for An. sinensis, 925 bp for An. koreicus, 650 bp for An. lindesayi, 527 bp for An. kleini, 436 bp for An. lesteri, 315 bp for An. sineroides, 260 bp for An. belenrae, and 157 bp for An. pullus. Conclusion A multiplex PCR assay was developed to identify Anopheles spp. distributed in the ROK. This method can be used to accurately identify Anopheles species that are difficult to identify morphologically to determine species distributions and malaria infection rates.

In a follow-up to the investigations of soft ticks identified from seabird nest soil and litter collected from coastal islands of the Republic of Korea (ROK), Ornithodoros sawaii and Ornithodoros capensis were assessed for the presence and identification of rickettsiae. Ticks collected from samples of 50–100 g of nest litter and soil from seabird nests were identified individually by morphological techniques, and species confirmed by sequencing of the mt-rrs gene. Subsequently, tick DNA preparations were screened for the presence of rickettsiae using a genus-specific nested PCR (nPCR) assay targeting the 17 kDa antigen gene. The amplicons from the 17 kDa assay and two additional nPCR assays targeting the gltA and ompB gene fragments were sequenced and used to identify the rickettsiae. A total of 134 soft ticks belonging to two species, O. sawaii Kitaoka & Suzuki 1973 (n = 125) and O. capensis Neumann 1901 (n = 9), were collected. Rickettsia lusitaniae DNA was detected and identified among O. sawaii ticks (n = 11, 8.8%) collected from nest litter and soil of the Japanese murrelet (Synthliboramphus wumizusume Temminck 1836) at Gugul Island along the western coastal area of the ROK. This study confirmed for the first time the presence of R. lusitaniae associated with O. sawaii collected from migratory seabird nests in the ROK.

Wing lengths of parous (P) and nulliparous (NP) PCR-identified female Anopheles belenrae, An. kleini, An. pullus, and An. sinensis were determined from weekly trap collections at Camp Humphreys (CH), Ganghwa Island (GH), and Warrior Base (WB), Republic of Korea (ROK) during Jun-Oct, 2009. Wing length was greatest at the beginning and end of the study period. Wing length of NPs tended to be less than that of Ps before the period of maximum greening (Jul-Aug) but greater thereafter. Larger specimens tended to be Ps, and weekly wing length of Ps appeared less variable than NPs, possibly due to selection. A bimodal wing length frequency distribution of An. sinensis suggested two forms comprising small- (≤4.5 mm, SW) and large-winged females (>4.5 mm, LW). LW comprised the majority of peaks in abundance, however %SW, while still a minority, often increased during these times suggesting a density-dependent effect. At WB and GH, a two to three-week periodicity in %SW was obvious for An. sinensis and An. kleini. Analyses of weather station and satellite data showed that smaller-winged An. sinensis were associated with warmer, more humid, and greener times of the year. SW and LW specimens possibly result from agricultural practices that are common across large areas; regular synchronous peaks of SW and LW were observed from different sites. Peaks in SW Ps followed peaks in NPs in a 'ripple effect' one to two weeks apart, suggesting that wing length combined with parity could be used to follow the emergence and survival of mosquito cohorts.

Aedes albopictus (Skuse) was first reported in the Republic of Korea in 1941 (Suwon, Gyeonggi Province). Recently, a mosquito-monitoring program was established in response to the potential development of autochthonous infections of dengue, chikungunya, and Zika viruses, to identify the regional characteristics of Ae. albopictus in Suwon. Daily collections of adult mosquitoes were conducted using Blackhole UV-LED traps and BG-Sentinel traps baited with octenol, carbon dioxide or both at five sites in Suwon (Sungkyunkwan University, Manseok, Seoho, Olympic, and Jungang parks) from 1 July to 1 November 2016. Based on the ecological cycle of mosquitoes, an estimated association between the daily mean temperatures [2 wk prior to the collection date (lag 2 wk)] and relative population abundance were developed using a generalized linear model. The overall proportion of female mosquitoes collected from all traps was 88.3%. Higher female trap indices were observed for mosquitoes collected at BG-Sentinel traps. Additionally, the BG-sentinel trap was more effective collecting Ae. albopictus. Culex pipiens (Coquillett) was the most frequently collected mosquito using UV-LED traps, followed by Ae. vexans nipponii (Theobald), Ochlerotatus koreicus (Edwards), Cx. inatomi (Kamimura and Wada), and members of the Anopheles Hyrcanus Group. Within a certain temperature range, daily mean temperatures 2 wk prior to the collection period was significantly associated with a maximum abundance of Ae. albopictus (P < 0.05) at 26.2°C (95% confidence interval: 24.3–29.4°C). The BG-Sentinel trap is an effective trap for monitoring relative population abundance of Ae. albopictus, and trap catches are significantly correlated with daily mean temperatures.

Pyrethroid (PYR) and organophosphate (OP) insecticides have been extensively used for mosquito control for several decades in South Korea, and has resulted in the rapid development of resistance in the field. In this study, quantitative sequencing (QS) protocols were developed for the frequency prediction of insecticide resistance alleles [e.g., the L1014F/C mutation on the voltage sensitive sodium channel as a PYR resistance allele and the G119S mutation on the acetylcholinesterase 1 as OP resistance alleles] in four regional populations of Anopheles Hyrcanus Group and Culex pipiens complex. Both of the L1014F/C and G119S mutations were observed in all examined regional populations of An. Hyrcanus Group, suggesting a wide distribution of both PYR and OP resistance. In contrast, populations of the Cx. pipiens complex were determined to possess almost no G119S mutation, but relatively higher frequencies of the L1014F mutation, showing differential resistance patterns between different mosquito groups. The mutation frequencies were also monitored throughout a mosquito season (May-October) at one collection site to determine the seasonal changes of resistance mutation frequency in mosquito populations. Dramatic decreases of both L1014F/C and G119S mutation frequencies were observed in the An. Hyrcanus Group toward the fall, with no mutations observed in the early spring, suggesting a connection between the fitness costs of overwintering and insecticide resistance. However, no apparent trends were detectable in the Cx. pipiens complex populations due to low or zero mutation frequencies.

Seoul virus (SEOV) poses a worldwide public health threat. This virus, which is harbored by Rattus norvegicus and R. rattus rats, is the causative agent of hemorrhagic fever with renal syndrome (HFRS) in humans, which has been reported in Asia, Europe, the Americas, and Africa. Defining SEOV genome sequences plays a critical role in development of preventive and therapeutic strategies against the unique worldwide hantavirus. We applied multiplex PCR–based next-generation sequencing to obtain SEOV genome sequences from clinical and reservoir host specimens. Epidemiologic surveillance of R. norvegicus rats in South Korea during 2000–2016 demonstrated that the serologic prevalence of enzootic SEOV infections was not significant on the basis of sex, weight (age), and season. Viral loads of SEOV in rats showed wide dissemination in tissues and dynamic circulation among populations. Phylogenetic analyses showed the global diversity of SEOV and possible genomic configuration of genetic exchanges.

Flaviviruses, for example, dengue virus (DENV) and Zika virus (ZIKV), and Alphaviruses, for example, chikungunya virus (CHIKV), attracted little attention until 2000 when increasingly higher numbers of infections were reported in urban settings throughout much of the tropical and subtropical areas of the world. While Aedes aegypti is the primary vector in most areas, Aedes albopictus, which is present in relatively high numbers in forested areas of the Republic of Korea (ROK), as well as limited urban environments (e.g., where used tires are improperly stored), is considered a secondary vector. Aedes albopictus gained considerable attention in 2016 when > 100 imported cases of DENV were reported annually since 2010 in the ROK as travelers returned home from endemic countries,1 in addition to 16 imported cases of ZIKV in 2016. ZIKV, a member of the Family Flaviviridae, was first isolated in Uganda, Africa, from monkeys in 1947 and from Aedes africanus in 1948.2 While there were occasional cases and outbreaks, its recent adaptation to efficiently infect Ae. aegypti, Ae. albopictus, and several other Aedes spp. in the Pacific Islands has led to its widespread dispersal and outbreaks in many of the tropical and semitropical regions of the world, including nine countries in Asia, 47 in Central and South America, one in North America, 10 in Oceania, and two in Africa, with the potential to spread to temperate regions during “mosquito seasons”.3–6 ZIKV is a monkey-mosquito-monkey forest cycle zoonotic disease that has been adapted to an urban Ae. aegypti-man-Ae. aegypti (and related Aedes species) cycle with the potential for emergence in nonendemic areas where competent mosquito vectors (e.g., Ae. albopictus) are present.7 Worldwide, Ae. aegypti, and Ae. albopictus to a lesser degree because of its broader range of hosts, have been identified as primary and secondary vectors of ZIKV.8 Vector competence studies of Ae. albopictus and Ae. aegypti exposed to the same mice infected by ZIKV showed that the viremia levels in mice produced disseminated infections. However, Ae. albopictus infection rates were more dose dependent, requiring higher blood meal titers than titers required for Ae. aegypti infections.9 Unfortunately, as with other arboviruses, for example, West Nile virus and CHIKV, there are no government approved human vaccines or other specific treatments for ZIKV.10 Therefore, it is essential to implement effective vector control for target species near residences where imported ZIKV-infected patients in the ROK are identified to decrease the potential human-vector-human transmission risks during the late spring to fall mosquito season. An example of this type of approach occurred in Chiba City, Japan, in 2014, when emergency vector surveillance and control strategies of Ae. albopictus were implemented due to local transmission of DENV. The result was that Ae. albopictus populations were significantly reduced after adult control strategies were implemented, which also reduced the risks for future transmission of DENV.11 A total of 16 imported ZIKV cases, including one asymptomatic case, were identified from January to October 2016 in the ROK. Nine of the cases were reported during the primary mosquito season from June to October.12 All ZIKV cases were attributed to transmission by mosquitoes during their travels to foreign ZIKV endemic countries, with 77% of the cases attributed to travel to Southeast Asia (Philippines, Vietnam, and Thailand).13 While the Korean Centers for Disease Control & Prevention (KCDC) has established vector control guidelines for vivax malaria and Japanese encephalitis that are endemic in the ROK, there were no established guidelines for vector control of nonendemic vector-borne diseases, for example, ZIKV, DENV, and CHIKV, imported from tropical and subtropical countries where they are endemic. To reduce the potential for autochthonous transmission of imported mosquito-borne viruses during the mosquito season in the ROK, the KCDC established guidelines in 2016 for the control of Ae. albopictus, the primary vector in Korea.4 However, the efficacies of these guidelines have not been fully evaluated.

Encounters with ticks harboring pathogenic agents have demonstrated increasing public health implications. Tick surveillance in the Republic of Korea (ROK) is essential for determining tick distributions and the potential regions where tick-borne pathogens may be found. Extensive tick collections (tick drags and tick flagging) were previously performed by Force Health Protection & Preventive Medicine (FHP&PM), Medical Activity-Korea (MEDDAC-K)/65th Medical Brigade (MED BDE) personnel, in collaboration with the Public Health Activity-Korea in the ROK. A total of 144,131 ticks were collected from 2,019 locations during 2004 to 2016. The associated location data (GPS coordinates) for each of the collection sites were incorporated into distribution maps using ArcGIS and combined with environmental data in the Maxent ecological niche modeling program (n = 733 geographical unique locations from 1,429 presence records/collection locations) to produce estimates of tick distributions for each species. The predominant tick species found and modeled were, in order of prevalence: Haemaphysalis longicornis, H. flava, Ixodes nipponensis, H. phasiana, I. turdus, Amblyomma testudinarium, H. japonica, and I. persulcatus. Haemaphysalis longicornis, H. flava, and I. nipponensis were the most widely distributed and most commonly collected species of ticks. The maps and models of suitable habitat regions produced in this study provide a better understanding of where there are potential risks of encountering a particular tick species, and which, as demonstrated herein with rickettsiae, can be used to study tick-pathogen dynamics of diseases. Knowledge of the distribution of ticks is important in the ROK because of the presence of tick-borne diseases, such as severe fever with thrombocytopenia syndrome, tick-borne encephalitis, rickettsioses, and borrelioses.

A Rickettsia sp. was isolated from the blood of a patient with an acute febrile illness using the shell vial technique; the isolate was named CN45Kr and was identified by molecular assay as Rickettsia monacensis, which was first recognized as a pathogen in Spain. Sequencing analysis showed that the gltA sequence of the isolate was identical to that of Rickettsia sp. IRS3. The ompA-5mp fragment sequence showed 100% identity to those of R. monacensis and Rickettsia sp. In56 and ompA-3pA In56 and 100% identity to that of Rickettsia sp. IRS3. The ompB sequence was found to have 99.9% similarity to that of R. monacensis IrR/Munich. This study confirms the pathogenicity of this agent and provides additional information about its geographic distribution.

Flaviviruses comprise a large and diverse group of positive-stranded RNA viruses, including tick-, mosquito- and unknown-vector-borne flaviviruses. A novel flavivirus was detected in pools of Aedes vexans nipponii (n=1) and Aedes esoensis (n=3) collected in 2012 and 2013 near the demilitarized zone (DMZ), Republic of Korea (ROK). Phylogenetic analyses of the NS5, E gene and complete polyprotein coding sequence (CDS) showed that the novel virus fell within the Aedes-borne flaviviruses (ABFVs), with nucleotide identity ranging from 57.8-75.1 %, 46.1-74.2 % and 51.1-76.2 %, respectively. While the novel ABFV was distant from other flaviviruses within the group, it formed a clade with Ilomantsi virus (ILOV). Sequence alignments of the partial NS5 gene, full-length E gene and polyprotein CDS between the novel virus and ILOV showed approximately 76.2 % nucleotide identity and 90 % amino acid identity, respectively. The ABFV identified in Aedes mosquitoes from the ROK is a novel ABFV based on the sequence analyses and is designated as Panmunjeom flavivirus (PANFV).

Orthohantaviruses are negative-sense, single-stranded RNA viruses harbored by rodents, shrews, moles, and bats. Of the shrew-borne orthohantaviruses in the Republic of Korea (ROK), Jeju orthohantavirus (Jeju virus, JJUV) was found on Jeju Island. This small-scale epidemiologic survey investigated the geographic distribution and molecular phylogeny of JJUV in the ROK. In 32 trapping sites, tissues of 84 Crocidura shantungensis were analyzed for JJUV RNA. JJUV RNA was detected in seven (8.3%) shrews captured on the Korean peninsula. The molecular epidemiologic survey demonstrated the prevalence of JJUV by geographic distribution. The RNA loads of JJUV were evaluated in various tissues. Entire coding sequences of tripartite genomes were recovered from two JJUV strains on the mainland. Phylogenetic relationships of the JJUV revealed a distinct geographic lineage of mainland strains from the strains on Jeju Island. This study sheds light on the molecular epidemiology, phylogeographic diversity, and virus-host co-divergence of JJUV, ROK.