Hard Ticks as Vectors Tested Negative for Severe Fever with Thrombocytopenia Syndrome in Ganghwa-do, Korea during 2019-2020

This study aimed to characterize the seasonal abundance of hard ticks that transmit severe fever with thrombocytopenia syndrome virus from April to November 2019 and 2020 on Ganghwa-do, Incheon Metropolitan City, Korea. The ticks were collected at grassland, grave site, copse and mountain road using a collection trap method. The ixodid hard ticks comprising three species (Haemaphysalis longicornis, H. flava, and Ixodes nipponensis) collected were 6,622 in 2019 and 3,811 in 2020. H. longicornis was the most frequent (97.9% in 2019 and 96.0% in 2020), followed by H. flava (2.0% and 3.0% in 2019 and 2020, respectively) and I. nipponensis (less than 0.1%). Our study demonstrated that seasonal patterns of the tick populations examined for two years were totally unsimilar. The hard ticks tested using RT-qPCR were all negative for severe fever with thrombocytopenia syndrome virus.

Hard Ticks as Vectors Tested Negative for Severe Fever with Thrombocytopenia Syndrome in Ganghwa-do, Korea during 2019-2020

This study aimed to characterize the seasonal abundance of hard ticks that transmit severe fever with thrombocytopenia syndrome virus from April to November 2019 and 2020 on Ganghwa-do, Incheon Metropolitan City, Korea. The ticks were collected at grassland, grave site, copse and mountain road using a collection trap method. The ixodid hard ticks comprising three species (Haemaphysalis longicornis, H. flava, and Ixodes nipponensis) collected were 6,622 in 2019 and 3,811 in 2020. H. longicornis was the most frequent (97.9% in 2019 and 96.0% in 2020), followed by H. flava (2.0% and 3.0% in 2019 and 2020, respectively) and I. nipponensis (less than 0.1%). Our study demonstrated that seasonal patterns of the tick populations examined for two years were totally unsimilar. The hard ticks tested using RT-qPCR were all negative for severe fever with thrombocytopenia syndrome virus.

Monitoring Culicine Mosquitoes (Diptera: Culicidae) as a Vector of Flavivirus in Incheon Metropolitan City and Hwaseong-Si, Gyeonggi-Do, Korea, during 2019

The flaviviruses are small single-stranded RNA viruses that are typically transmitted by mosquitoes or tick vectors and are etiological agents of acute zoonotic infections. The viruses are found around the world and account for significant cases of human diseases. We investigated population of culicine mosquitoes in central region of Korean Peninsula, Incheon Metropolitan City and Hwaseong-si. Aedes vexans nipponii was the most frequently collected mosquitoes (56.5%), followed by Ochlerotatus dorsalis (23.6%), Anopheles spp. (10.9%), and Culex pipiens complex (5.9%). In rural regions of Hwaseong, Aedes vexans nipponii was the highest population (62.9%), followed by Ochlerotatus dorsalis (23.9%) and Anopheles spp. (12.0%). In another rural region of Incheon (habitat of migratory birds), Culex pipiens complex was the highest population (31.4%), followed by Ochlerotatus dorsalis (30.5%), and Aedes vexans vexans (27.5%). Culex pipiens complex was the predominant species in the urban region (84.7%). Culicine mosquitoes were identified at the species level, pooled up to 30 mosquitoes each, and tested for flaviviral RNA using the SYBR Green-based RT-PCR and confirmed by cDNA sequencing. Three of the assayed 2,683 pools (989 pools without Anopheles spp.) were positive for Culex flaviviruses, an insect-specific virus, from Culex pipiens pallens collected at the habitats for migratory birds in Incheon. The maximum likelihood estimation (the estimated number) for Culex pipiens pallens positive for Culex flavivirus was 25. Although viruses responsible for mosquito-borne diseases were not identified, we encourage intensified monitoring and long-term surveillance of both vector and viruses in the interest of global public health.

Surveillance of Chigger Mite Vectors for Tsutsugamushi Disease in the Hwaseong Area, Gyeonggi-do, Republic of Korea, 2015

Owing to global climate change, the global resurgence of vector-borne infectious diseases and their potential to inflict widespread casualties among human populations has emerged as a pivotal burden on public health systems. Tsutsugamushi disease (scrub typhus) in the Republic of Korea is steadily increasing and was designated as a legal communicable disease in 1994. The disease is a mite-borne acute febrile disease most commonly contracted from October to December. In this study, we tried to determine the prevalence of tsutsugamushi disease transmitted by chigger mites living on rodents and investigated their target vector diversity, abundance, and distribution to enable the mapping of hotspots for this disease in 2015. A total of 5 species belonging to 4 genera (109 mites): Leptotrombidium scutellare 60.6%, L. pallidum 28.4% Neotrombicula tamiyai 9.2%, Euschoengastia koreaensis/0.9%), and Neoschoengastia asakawa 0.9% were collected using chigger mite collecting traps mimicking human skin odor and sticky chigger traps from April to November 2015. Chigger mites causing tsutsugamushi disease in wild rodents were also collected in Hwaseong for the zoonotic surveillance of the vector. A total of 77 rodents belonging to 3 genera: Apodemus agrarius (93.5%), Crocidura lasiura (5.2%), and Micromys minutus (1.3%) were collected in April, October, and November 2015. The most common mite was L. pallidum (46.9%), followed by L. scutellare (18.6%), and L. orientale (18.0%). However, any of the chigger mite pools collected from rodent hosts was tested positive for Orientia tsutsugamushi, the pathogen of tsutsugamushi disease, in this survey.

Four Year Surveillance of the Vector Hard Ticks for SFTS, Ganghwa-do, Republic of Korea

The seasonal abundance of hard ticks that transmit severe fever with thrombocytopenia syndrome virus was monitored with a collection trap method every April to November during 2015–2018 and with a flagging method every July and August during 2015–2018 in Ganghwa-do (island) of Incheon Metropolitan City, Republic of Korea. This monitoring was performed in a copse, a short grass field, coniferous forest and broad-leaved forest. A total of 17,457 ticks (8,277 larvae, 4,137 nymphs, 3,389 females, and 1,654 males) of the ixodid ticks comprising 3 species (Haemaphysalis longicornis, H. flava, and Ixodes nipponensis) were collected with collection traps. Of the identified ticks, H. longicornis was the most frequently collected ticks (except larval ticks) (94.26%, 8,653/9,180 ticks (nymphs and adults)), followed by H. flava (5.71%, 524/9,180) and Ix. nipponensis (less than 0.04%, 3/9,180). The ticks collected with collecting traps were pooled and assayed for the presence of SFTS virus with negative results. In addition, for monitoring the prevalence of hard ticks, a total of 7,461 ticks (5,529 larvae, 1,272 nymphs, 469 females, and 191 males) of the ixodid ticks comprising 3 species (H. longicornis, H. flava, and Ix. nipponensis) were collected with flagging method. H. longicornis was the highest collected ticks (except larval ticks) (99.53%, 1,908/1,917 ticks (nymphs and adults)), followed by H. flava (1.15%, 22/1,917).

Molecular Epidemiologic Investigation of Norovirus Infections in Incheon City, Korea, from 2005 to 2007

Noroviruses (NoVs) cause major epidemic gastroenteritis in humans. To obtain the molecular epidemiological information on gastroenteritis sporadic cases in Incheon city, Korea, we analyzed the nucleotide sequences of NoV strains detected during 2005~2007. We performed one step RT-PCR amplifying the open reading frame (ORF) 2 (capsid region) followed by semi-nested PCR from the stool samples from acute gastroenteritis patients from 2005 to 2007. Amplicons of the capsid region of norovirus strains were sequenced and analyzed using MegAlign in DNAstar software. Faecal samples were collected from 6,618 acute gastroenteritis patients during the study period. The incidence of NoV infection was about 10.7% (n=708) among patients with acute gastroenteritis and genotypes of the 320 positive samples were determined by sequence analysis. Sequence comparison of NoV strains revealed that 16 genotypes of GII NoV strains were circulated in Incheon city, from 2005 to 2007. Among norovirus strains, the most prevalent genotype GII/4 was most common 69.7% (223 strains), followed by GII/3 17.2% (55 strains), GII/12 4.4% (14 strains), GII/1 2.2% (7 strains), GII/5 1.6% (5 strains), GII/15 1.3% (4 strains) and 0.6% (2 strains) each of GII/9 and GII/16. The GII-3 strains were most frequently detected in Incheon, 2005. From the phylogenetic analysis of NoV strains, we detected 16 genotypes of GII NoV strains during 2005~2007 in Incheon. Our results suggest that various genotypes of human NoV strains in sporadic case of AGE were circulated in Incheon, Korea.

Epidemiological Analysis of Influenza by Laboratory Surveillance in Incheon, 2003/2004~2004/2005 / 대한임상미생물학회지

BACKGROUND: Influenza is a highly contagious respiratory disease. Influenza virus, which causes epidemics every winter season, has the high possibility of appearing with new virus types every year due to antigen variation. Therefore, we intended to analyze the data on the epidemiology of influenza that had been acquired by laboratory surveillance in Incheon during the 2003/2004 and 2004/ 2005 seasons and to apply the knowledge to the control and prevention of influenza in Korea. METHODS: Specimens were inoculated into Madin-Darby canine kidney (MDCK) cells and, when cytopathic effect (CPE) was seen, culture supernatants were tested by mutiplex RT-PCR for typing and subtyping of influenza viruses. RESULTS: The first virus of the season was isolated at week 47 (3rd week on November) in 2003 during 2003/2004 and at week 43 (4th week on October) in 2004 during 2004/2005, which was about 4 weeks earlier than in the 2003/2004 season. From 532 specimens cultured for influenza virus during the 2003/2004 season. 330 (62.0%) viruses were isolated: 161 (48.8%) A/H3N2, 1 (0.3%) A/H1N1, and 168 (50.9%) B. During 2004/2005 season, 457 specimens were tested and 278 (60.8 %) were positive for influenza virus: 232 (83.5%) A/H3N2, 5 (1.8%) A/H1N1, and 38 (13.7%) B. The incidence of influenza was the highest in the school-age children and young adults of 7 to 19 years age group in both seasons. CONCLUSION: Influenza virus was isolated at a high rate (more than 60%) by the laboratory influenza surveillance system in Incheon during the 2003/2004 and 2004/2005 seasons: the predominant strain was influenza A/H3N2 subtype.