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  1. [Nipah virus outbreak in Malaysia, 1999]
    Okabe N, Morita K
    Uirusu, 2000 Jun;50(1):27-33.
    PMID: 10998976
  2. Oligonucleotide fingerprint analysis of strains of Getah virus isolated in Japan and Malaysia
    Morita K, Igarashi A
    J Gen Virol, 1984 Nov;65 ( Pt 11):1899-908.
    PMID: 6094708
    Eighteen strains of Getah virus isolated from mosquitoes, swine and horses in Japan (1956 to 1981), and one strain isolated in Malaysia (1955), were analysed by RNase T1-resistant oligonucleotide fingerprinting. All fingerprints showed a poly(A) tract. The fingerprint pattern of the Malaysian strain was quite different from those of the Japanese strains. Although most of the recent Japanese isolates shared many large oligonucleotide spots in common, the patterns were not identical even among the strains obtained in one locality in the same year. These results suggest that the Getah virus genome undergoes mutation rather frequently. However, there is a tendency for the isolates of the same year to show greater similarity. The fingerprint patterns of certain host-dependent temperature-sensitive (ts) mutants differed from that of the parental strain. Also, there were some differences in large oligonucleotide spots between strain JaNAr12380M isolated in suckling mouse brain (SMB) and strain JaNAr12380A isolated in C6/36 cells, despite the fact that both strains were derived from the same wild mosquito homogenate. In addition, many host-dependent ts mutants were present in strain JaNAr12380A, whereas no such mutants were observed in strain JaNAr12380M. It is concluded that there is considerable variation in the strains of Getah virus infecting mosquitoes in the wild, and also that the variants or mutants present in mosquitoes might be subject to selection during viral multiplication in the mammalian host.
  3. Sequences of E/NS1 gene junction from four dengue-2 viruses of northeastern Thailand and their evolutionary relationships with other dengue-2 viruses
    Zin K, Morita K, Igarashi A
    Microbiol. Immunol., 1995;39(8):581-90.
    PMID: 7494497
    We determined the 240-nucleotide sequences of the E/NS1 gene junction of four dengue-2 viruses by the primer extension dideoxy chain termination method. These viruses were isolated from dengue patients with different clinical severities in Nakhon Phanom, Northeastern Thailand in 1993. The results were compared with the 52 published dengue-2 sequences of the same gene region. Sequence divergence of four new isolates varied from 4.17% to 5.42% compared with dengue-2 prototype New Guinea C strain whereas it varied from 5.42% to 6.67% and from 6.67% to 7.09% when compared with Jamaica 1409 strain and PR159/S1 strain, respectively. All nucleotide substitutions were found at the 3rd position of the codons which were silent mutations. All 56 isolates studied were classified into five genotypic groups by constructing the dendrogram. The results indicated that four new isolates from Northeastern Thailand belong to genotype II of dengue virus serotype 2, and were most closely related to prototype New Guinea C strain. We also observed the variation in nucleotide and amino acid sequences among clusters of isolates (Thailand-1980, Malaysia-1989 and Thailand-1993) which were obtained from the dengue patients with different clinical severities. The significance of these genetic differences have been discussed in terms of the possible correlation between genetic variability and virulence.
  4. Fulltext Comparison of sequences of E/NS1 gene junction of dengue type 3 virus following culture subpassage in C6/36 cells to study the possible occurrence of mutations
    Thayan R, Morita K, Vijayamalar B, Zainah S, Chew TK, Oda K, et al.
    Southeast Asian J. Trop. Med. Public Health, 1997 Jun;28(2):380-6.
    PMID: 9444025
    The aim of this study was to determine whether mutations could occur in the dengue virus genome following three subpassages of the virus in a mosquito cell line. This was done because sources of virus isolates used for sequencing studies are usually maintained in cell lines rather than in patients' sera. Therefore it must be assured that no mutation occurred during the passaging. For this purpose, sequencing was carried out using the polymerase chain reaction (PCR) products of the envelope/non-structural protein 1 junction region (280 nucleotides) of dengue type 3 virus. Sequence data were compared between the virus from a patient's serum against the virus subpassaged three times in the C6/36 cell line. We found that the sequence data of the virus from serum was identical to the virus that was subpassaged three times in C6/36 cell line.
  5. The use of polymerase chain reaction (PCR) as a diagnostic tool for dengue virus
    Thayan R, Vijayamalar B, Zainah S, Chew TK, Morita K, Sinniah M, et al.
    Southeast Asian J. Trop. Med. Public Health, 1995 Dec;26(4):669-72.
    PMID: 9139373
    This study describes the use of polymerase chain reaction as a diagnostic tool for detecting and typing of dengue virus. PCR was compared against virus isolation. First RT-PCR was done using dengue consensus primers after which positive samples were subjected to RT-PCR using type-specific primers. This study shows that the local strains of the dengue virus could be detected using the chosen primers. Furthermore, RT-PCR was found to be more sensitive than virus isolation in identifying the dengue positive samples.
  6. Isolation of Japanese encephalitis virus from mosquitoes collected in Sabak Bernam, Selangor, Malaysia in 1992
    Vythilingam I, Oda K, Chew TK, Mahadevan S, Vijayamalar B, Morita K, et al.
    J Am Mosq Control Assoc, 1995 Mar;11(1):94-8.
    PMID: 7616198
    Detection and isolation of Japanese encephalitis (JE) virus were attempted from female mosquitoes collected in Kampong Pasir Panjang, Sabak Bernam, Selangor, from May to November 1992. A total of 7,400 mosquitoes consisting of 12 species in 148 pools were processed and inoculated into Aedes albopictus clone C6/36 cell cultures. Of these, 26 pools showed the presence of viral antigens in the infected C6/36 cells by specific immunoperoxidase staining using an anti-JE virus polyclonal antibody. Presence of JE virus genome was confirmed in the infected culture fluid for 16 pools by using reverse transcriptase-polymerase chain reaction and JE virus-specific primers. Of these, 3 pools were from Culex tritaeniorhynchus, 4 from Culex vishnui, 3 from Culex bitaeniorhynchus, 2 from Culex sitiens, one from Aedes species, and 3 from Culex species. Isolation of JE virus from Cx. sitiens, Cx. bitaeniorhynchus, and Aedes sp. (Aedes butleri and Ae. albopictus) is reported for the first time in Malaysia.
  7. Fulltext Different IVIG glycoforms affect in vitro inhibition of anti-ganglioside antibody-mediated complement deposition
    Sudo M, Yamaguchi Y, Späth PJ, Matsumoto-Morita K, Ong BK, Shahrizaila N, et al.
    PLoS One, 2014;9(9):e107772.
    PMID: 25259950 DOI: 10.1371/journal.pone.0107772
    Intravenous immunoglobulin (IVIG) is the first line treatment for Guillain-Barré syndrome and multifocal motor neuropathy, which are caused by anti-ganglioside antibody-mediated complement-dependent cytotoxicity. IVIG has many potential mechanisms of action, and sialylation of the IgG Fc portion reportedly has an anti-inflammatory effect in antibody-dependent cell-mediated cytotoxicity models. We investigated the effects of different IVIG glycoforms on the inhibition of antibody-mediated complement-dependent cytotoxicity. Deglycosylated, degalactosylated, galactosylated and sialylated IgG were prepared from IVIG following treatment with glycosidases and glycosyltransferases. Sera from patients with Guillain-Barré syndrome, Miller Fisher syndrome and multifocal motor neuropathy associated with anti-ganglioside antibodies were used. Inhibition of complement deposition subsequent to IgG or IgM autoantibody binding to ganglioside, GM1 or GQ1b was assessed on microtiter plates. Sialylated and galactosylated IVIGs more effectively inhibited C3 deposition than original IVIG or enzyme-treated IVIGs (agalactosylated and deglycosylated IVIGs). Therefore, sialylated and galactosylated IVIGs may be more effective than conventional IVIG in the treatment of complement-dependent autoimmune diseases.
  8. Combined detection and genotyping of Chikungunya virus by a specific reverse transcription-polymerase chain reaction
    Hasebe F, Parquet MC, Pandey BD, Mathenge EG, Morita K, Balasubramaniam V, et al.
    J Med Virol, 2002 Jul;67(3):370-4.
    PMID: 12116030
    A reverse transcription-polymerase chain reaction (RT-PCR) was developed for the detection of Chikungunya virus infection. Based on the nonstructural protein 1 (nsP1) and glycoprotein E1 (E1) genes of Chikungunya, two primer sets were designed. Total RNA were extracted from the cell culture fluid of Aedes albopictus C6/36 cells inoculated with the S27 prototype virus, isolated in Tanzania in 1953, and the Malaysian strains (MALh0198, MALh0298, and MALh0398), isolated in Malaysia in 1998. For both sets of RNA samples, the expected 354- and 294-base pair (bp) cDNA fragments were amplified effectively from the nsP1 and E1 genes, respectively. Phylogenetic analysis was conducted for the Malaysian strain and other virus strains isolated from different regions in the world endemic for Chikungunya, using partial E1 gene sequence data. The Malaysian strains isolated during the epidemics of 1998 fell into a cluster with other members of the Asian genotype.
  9. Fulltext Emergence of Genotype I of Dengue Virus Serotype 3 during a Severe Dengue Epidemic in Sri Lanka in 2017
    Ngwe Tun MM, Muthugala R, Rajamanthri L, Nabeshima T, Buerano CC, Morita K
    Jpn J Infect Dis, 2021 Sep 22;74(5):443-449.
    PMID: 33642435 DOI: 10.7883/yoken.JJID.2020.854
    During the 2017 outbreak of severe dengue in Sri Lanka, dengue virus (DENV) serotypes 2, 3, and 4 were found to be co-circulating. Our previous study of 295 patients from the National Hospital Kandy in Sri Lanka between March 2017 and January 2018 determined that the dominant infecting serotype was DENV-2. In this study, we aimed to characterize the DENV-3 strains from non-severe and severe dengue patients from our previous study population. Patients' clinical records and previous laboratory tests, including dengue-specific nonstructural protein 1 antigen rapid test and IgM-capture and IgG enzyme-linked immunosorbent assays, were analyzed together with the present results of real-time reverse transcription polymerase chain reaction and next-generation sequencing of DENV-3. Complete genome analysis determined that DENV-3 isolates belonged to 2 different clades of genotype I and were genetically close to strains from Indonesia, China, Singapore, Malaysia, and Australia. There were 16 amino acid changes among DENV-3 isolates, and a greater number of changes were found in nonstructural proteins than in structural proteins. The emergence of DENV-3 genotype I was noted for the first time in Sri Lanka. Continuous monitoring of this newly emerged genotype and other DENV serotypes and genotypes is needed to determine their effects on future outbreaks and understand the molecular epidemiology of dengue.
  10. Fulltext Acceptance and Preference for COVID-19 Vaccine among Japanese Residents at Early Stage of the Epidemic in Japan
    Wu J, Cai G, Fan Y, Arima K, Lin Y, Wong L, et al.
    Vaccines (Basel), 2023 Jan 11;11(1).
    PMID: 36680002 DOI: 10.3390/vaccines11010157
    Background: This study aimed to survey the attitudes toward COVID-19 vaccines and their acceptability among the Japanese public as soon as the United States Food and Drug Administration (FDA) authorized vaccines and their rollouts started around the world. Methods: An anonymous cross-sectional survey was conducted in Japan between 4 January and 5 March 2021. A questionnaire was administered to evaluate attitudes toward COVID-19 vaccines according to demographic characteristics, vaccine characteristics, and vaccine production. Results: A total of 1037 completed responses were received. More than half (63.5%) of the participants responded positively (extremely likely/likely) toward COVID-19 vaccines. The highest acceptance to be vaccinated was discovered among the youngest age group. As expected, participants who had never delayed acceptance or refused the vaccine in their history of vaccination had a significantly higher willingness to be vaccinated against COVID-19 (p < 0.001). Females (OR = 2.66, 95% CI: 1.99−3.58) and participants who had ever delayed acceptance or refuse the vaccine (OR = 3.49, 95% CI: 2.42−5.05) had higher odds of COVID-19 vaccine hesitancy. Participants with a postgraduate degree (OR = 0.64, 95% CI: 0.40−1.00) presented the highest willingness to be vaccinated against COVID-19. More than two-thirds (72.9%, 95% CI: 70.4%−75.8%) of the participants did not mind a booster dose required following primary vaccination. A total of 63.2% (95% CI: 60.0%−66.0%) of the participants only accepted a nearly 90% effective or above vaccine at preventing COVID-19. At the same, 86.4% (95% CI: 84.4%−88.4%) of the participants reported only accepting a vaccine with minor side effects. Conclusions: The moderate levels of COVID-19 vaccine acceptance found in the early phase of the pandemic demonstrate that it is important to improve the implementation of effective management for vaccine promotion and the acceptability of the vaccine to slow or delay transmission.
  11. Fulltext Complete genome analysis and characterization of neurotropic dengue virus 2 cosmopolitan genotype isolated from the cerebrospinal fluid of encephalitis patients
    Ngwe Tun MM, Muthugala R, Nabeshima T, Soe AM, Dumre SP, Rajamanthri L, et al.
    PLoS One, 2020;15(6):e0234508.
    PMID: 32555732 DOI: 10.1371/journal.pone.0234508
    Dengue virus (DENV) infection remains a major public health concern in many parts of the world, including Southeast Asia and the Americas. Sri Lanka experienced its largest dengue outbreak in 2017. Neurological symptoms associated with DENV infection have increasingly been reported in both children and adults. Here, we characterize DENV type 2 (DENV-2) strains, which were isolated from cerebrospinal fluid (CSF) and/or serum of patients with dengue encephalitis. Acute serum and CSF samples from each patient were subjected to dengue-specific non-structural protein 1 (NS1) antigen test, IgM and IgG enzyme-linked immunosorbent assay (ELISA), virus isolation, conventional and real-time polymerase chain reaction (PCR), and next-generation sequencing (NGS). Among the 5 dengue encephalitis patients examined, 4 recovered and 1 died. DENV-2 strains were isolated from serum and/or CSF samples of 3 patients. The highest viral genome levels were detected in the CSF and serum of the patient who succumbed to the illness. A phylogenetic tree revealed that the DENV-2 isolates belonged to a new clade of cosmopolitan genotype and were genetically close to strains identified in China, South Korea, Singapore, Malaysia, Thailand, and the Philippines. According to the NGS analysis, greater frequencies of nonsynonymous and synonymous mutations per gene were identified in the nonstructural genes. The full genomes of serum- and CSF-derived DENV-2 from the same patient shared 99.7% similarity, indicating that the virus spread across the blood-brain barrier. This is the first report to describe neurotropic DENV-2 using whole-genome analysis and to provide the clinical, immunological, and virological characteristics of dengue encephalitis patients during a severe dengue outbreak in Sri Lanka in 2017.
  12. Fulltext Behavioural responses and anxiety symptoms during the coronavirus disease 2019 (COVID-19) pandemic in Japan: A large scale cross-sectional study
    Cai G, Lin Y, Lu Y, He F, Morita K, Yamamoto T, et al.
    J Psychiatr Res, 2021 Apr;136:296-305.
    PMID: 33631655 DOI: 10.1016/j.jpsychires.2021.02.008
    BACKGROUND: This study explored the behavioural responses and anxiety symptoms of the general adult population in Japan during the ongoing coronavirus disease 2019 (COVID-19) outbreak.

    METHODS: A web-based cross-sectional survey was conducted between 12th and May 13, 2020. Quota sampling was used to attain equal gender and age distributions representative of the Japanese population.

    RESULTS: A total of 4127 complete responses were analysed. Higher educational level (B = 0.045, p = 0.002) and household income (B = 0.04, p = 0.009) were associated with a higher increase in preventive measures when comparing before and after the state of emergency was declared. The highest reported social anxiety was a feeling of fear (65.6%), followed by embarrassment (43.8%), keeping infection a secret (41.3%), avoidance (41.3%), and stigma (25.5%). A total of 86.1% of the respondents reported moderate to severe anxiety. The partial least square-based structural equation modelling (PLS-SEM) revealed that being female has the greatest effect (B = 0.246, p 

  13. Unusual, neurological and severe dengue manifestations during the outbreak in Sri Lanka, 2017
    Ngwe Tun MM, Muthugala R, Nabeshima T, Rajamanthri L, Jayawardana D, Attanayake S, et al.
    J Clin Virol, 2020 04;125:104304.
    PMID: 32145478 DOI: 10.1016/j.jcv.2020.104304
    BACKGROUND: Sri Lanka experienced its largest dengue outbreak in 2017 with more than 185,000 dengue cases including at least 250 fatalities.

    OBJECTIVES: Our study aimed to characterize the clinical, immunological and virological features of confirmed dengue patients in Sri Lanka during the outbreak in 2017 when unusual manifestations of severe dengue were observed.

    STUDY DESIGN: Sera from 295 patients who were admitted to Teaching Hospital Kandy, Kandy, Sri Lanka between March 2017- January 2018 were subjected to NS1 antigen, IgM and IgG ELISAs, virus isolation, conventional and real time RT-PCR and next generation sequencing.

    RESULTS: Primary and secondary infections were detected in 48.5 % and 51.5 % of the study population, respectively. Two hundred twenty five DENV strains were isolated (219 DENV-2, one DENV-3, two DENV-4, two mixed infections of DENV-2 and -3 and one mixed infection of DENV-2 and -4). Unusual and severe manifestations such as encephalitis, encephalopathy, liver failure, kidney failure, myocarditis, Guillain-Barré syndrome and multi-organ failure were noted in 44 dengue patients with 11 deaths. The viraemia levels in patients with primary infection and unusual manifestations were significantly higher compared to those in patients with secondary infection. A new clade of DENV-2 Cosmopolitan genotype strains was observed with the strains closely related to those from China, Malaysia, Indonesia, Singapore and Taiwan.

    CONCLUSIONS: The new clade of DENV-2 cosmopolitan genotype observed in Sri Lanka in 2017 caused an unprecedented, severe dengue outbreak. The emergence of DENV-3 and DENV-4 in the 2017 outbreak might cause future outbreaks in Sri Lanka.

  14. Fulltext Serological Evidence of Zika Virus Infection in Febrile Patients and Healthy Blood Donors in Sabah, Malaysian Borneo, 2017-2018
    Ngwe Tun MM, Mori D, Sabri SB, Kugan O, Shaharom SB, John J, et al.
    Am J Trop Med Hyg, 2021 Nov 22;106(2):601-606.
    PMID: 34814105 DOI: 10.4269/ajtmh.21-0802
    Several Zika virus (ZIKV) seroprevalence studies have been conducted in Africa, Asia, Oceania, the Americas, and the Caribbean. However, studies on ZIKV seroprevalence are limited in Malaysia though several studies have shown that the disease is endemic in the Malaysian state of Sabah. To evaluate the seroprevalence of ZIKV infection, 818 serum samples were collected from febrile patients and healthy blood donors from the Kudat and Kota Kinabalu districts in Sabah from 2017 to 2018. They were screened for ZIKV infection by IgM and IgG ELISA, and positive ZIKV IgM samples were subjected to a 90% neutralization test for confirmation. Twenty-four (6% [95% CI 4 to 8]) confirmed and two (0.5% [95% CI 0.13 to 1.8]) probable ZIKV infections were detected among 400 febrile illness patients. Of 418 healthy blood donor samples, six (1.4% [95% CI 0.65 to 3]) were determined as confirmed ZIKV infections and six (1.4% [95% CI 0.65 to 3]) indicated probable ZIKV infection. This is the first study on the seroprevalence of ZIKV infections among patients and healthy blood donors in Sabah. Compared with previous studies in Malaysia, this study shows that the incidence of ZIKV infection has increased. It also suggests that a sero-surveillance system is essential to determine the circulation of ZIKV in Sabah, Malaysia.
  15. Fulltext Detection of east/central/south African genotype of chikungunya virus in Myanmar, 2010
    Tun MM, Thant KZ, Inoue S, Nabeshima T, Aoki K, Kyaw AK, et al.
    Emerg Infect Dis, 2014 Aug;20(8):1378-81.
    PMID: 25062511 DOI: 10.3201/eid2008.131431
    In 2010, chikungunya virus of the East Central South African genotype was isolated from 4 children in Myanmyar who had dengue-like symptoms. Phylogenetic analysis of the E1 gene revealed that the isolates were closely related to isolates from China, Thailand, and Malaysia that harbor the A226V mutation in this gene.
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