Anopheles sinensis Wiedemann (63.3%) was the most abundant Anopheles mosquito captured at cowshed resting collections in malaria high-risk areas (northern Gyeonggi Province) near the demilitarized zone (DMZ) in Korea during 2005, followed by Anopheles kleini Rueda (24.7%) and Anopheles pullus M. Yamada (8.7%). At cowshed resting collections in malaria low-risk areas (Jeonnam and Gyeongnam provinces), An. sinensis accounted for 96.8% of all Anopheles spp. collected, followed by An. kleini Rueda (2.7%), whereas no An. pullus were collected. Three species, An. kleini (50.9%), An. pullus (29.0%), and An. sinensis (13.8%), accounted for nearly all of the 224 Anopheles spp. captured by New Jersey light trap near the DMZ. In addition, An. pullus and An. kleini captured by New Jersey light trap near the DMZ and assayed by enzyme linked immunosorbent assay for Plasmodium vivax circumsporozoite antigen concentrations were higher than An. sinensis sensu stricto (s.s.), indicating higher levels of sporozoites. In laboratory studies of four concurrent artificial membrane feedings on malaria-infected blood from patients, F1 progeny of An. kleini and An. pullus had higher infection rates (8.8 and 7.5%, respectively) than An. sinensis s.s. (4.2%). These data suggest that An. kleini and An. pullus and An. sinensis are vectors of malaria in Korea. Further studies are required to determine the role of these species in the transmission of P. vivax in the Republic of Korea.

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Ticks play an important role in transmission of arboviruses responsible for emerging infectious diseases, and have a significant impact on human, veterinary, and wildlife health. In the Republic of Korea (ROK), little is known about information regarding the presence of tick-borne viruses and their vectors. A total of 21,158 ticks belonging to 3 genera and 6 species collected at 6 provinces and 4 metropolitan areas in the ROK from March to October 2014 were assayed for selected tick-borne pathogens. Haemaphysalis longicornis (n=17,570) was the most numerously collected, followed by Haemaphysalis flava (n=3317), Ixodes nipponensis (n=249), Amblyomma testudinarium (n=11), Haemaphysalis phasiana (n=8), and Ixodes turdus (n=3). Ticks were pooled (adults 1-5, nymphs 1-30, and larvae 1-50) and tested by one-step reverse transcription polymerase chain reaction (RT-PCR) or nested RT-PCR for the detection of severe fever with thrombocytopenia virus (SFTSV), tick-borne encephalitis virus (TBEV), Powassan virus (POWV), Omsk hemorrhagic fever virus (OHFV), and Langat virus (LGTV). The overall maximum likelihood estimation (MLE) [estimated numbers of viral RNA positive ticks/1000 ticks] for SFTSV and TBEV was 0.95 and 0.43, respectively, while, all pools were negative for POWV, OHFV, and LGTV. The purpose of this study was to determine the prevalence of SFTSV, TBEV, POWV, OHFV, and LGTV in ixodid ticks collected from vegetation in the ROK to aid our understanding of the epidemiology of tick-borne viral diseases. Results from this study emphasize the need for continuous tick-based arbovirus surveillance to monitor the emergence of tick-borne diseases in the ROK.

Arboviruses continue to be a significant global health concern. The unbiased metagenomic analyses of mosquito-borne and mosquito-specific viruses are useful to understand viral diversity and for the surveillance of pathogens of medical and veterinary importance. Metagenomic analysis was conducted on 6368 mosquitoes (736 pools), covering 16 species from 18 locations throughout the Republic of Korea (ROK) in 2016. In this report, we describe three viruses detected in a single pool of Aedes vexans nipponii collected at Yongsan U.S. Army Garrison, located in a densely populated district of Seoul, the ROK. The three novel viruses, designated as Yongsan bunyavirus 1 (YBV1), Yongsan picorna-like virus 3 (YPLV3) and Yongsan sobemo-like virus 1 (YSLV1), share sequence and structural characteristics with members belonging to the family Bunyaviridae, order Picornavirales, and family Solemoviridae, with shared RNA-dependent RNA polymerase (RdRp) amino acid identities of 40%, 42% and 86%, respectively. The real-time reverse transcription and polymerase chain reaction (RT-PCR) of 3493 Aedes vexans nipponii (257 pools) showed a high prevalence of YBV1 and YSLV1 viruses, which were present in 65% and 62% of tested pools, respectively. This study highlighted the utility of a metagenomic sequencing approach for arbovirus discovery and for a better understanding of the virome of potential medically relevant vectors.

Malaria was eradicated and the Republic of Korea (ROK) declared "malaria free" in 1979. However, in 1993, a temperate strain of vivax malaria, expressing both latent and nonlatent disease populations, re-emerged near the demilitarized zone (DMZ), rapidly spread to civilian sectors near the DMZ, and increased exponentially in ROK military, veteran, and civilian populations through 1998. Malaria among all ROK populations decreased 5-fold from a high of 4142 cases in 2000 to a low of 826 cases in 2004, before increasing again to 2180 cases by 2007. Each malaria case in the ROK is reported in the metropolitan area/province where the diagnosis is made, which may be at some distance from the area where infection occurred. Therefore, it is difficult to ascertain transmission sites since approximately 60% of vivax malaria in Korea is latent with symptoms occurring >1 month to 24 months after infection. A review of case diagnosis for civilian, veteran, and military populations shows that nearly all malaria south of Gyeonggi and Gangwon Provinces is the result of veterans exposed in malaria high-risk areas along the DMZ and returning to their hometowns where they later develop malaria. Thus, malaria currently remains localized near the DMZ with limited transmission in provinces south of Seoul and has not spread throughout Korea as previously hypothesized. This report describes the reemergence of vivax malaria cases in civilian and military ROK populations and U.S. military personnel and assesses variables related to its transmission and geographic distribution.