Displaying publications 21 - 40 of 261 in total

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  1. Fulltext Geographic distribution of Tick-borne encephalitis virus complex
    Im JH, Baek JH, Durey A, Kwon HY, Chung MH, Lee JS
    J Vector Borne Dis, 2020 1 1;57(1):14-22.
    PMID: 33818450 DOI: 10.4103/0972-9062.308794
    A comprehensive understanding of the geographic distribution of the tick-borne encephalitis virus (TBEV) complex is necessary due to increasing transboundary movement and cross-reactivity of serological tests. This review was conducted to identify the geographic distribution of the TBEV complex, including TBE virus, Alkhurma haemorrhagic fever virus, Kyasanur forest disease virus, louping-ill virus, Omsk haemorrhagic fever virus, and Powassan virus. Published reports were identified using PubMed, EMBASE, and the Cochrane library. In addition to TBEV complex case-related studies, seroprevalence studies were also retrieved to assess the risk of TBEV complex infection. Among 1406 search results, 314 articles met the inclusion criteria. The following countries, which are known to TBEV epidemic region, had conducted national surveillance studies: Austria, China, Czech, Denmark, Estonia, Finland, Germany, Hungary, Italy, Latvia, Norway, Poland, Romania, Russia, Switzerland, Sweden, Slovenia, and Slovakia. There were also studies/reports on human TBEV infection from Belarus, Bulgaria, Croatia, France, Japan, Kyrgyzstan, Netherland, and Turkey. Seroprevalence studies were found in some areas far from the TBEV belt, specifically Malaysia, Comoros, Djibouti, and Kenya. Kyasanur forest disease virus was reported in southwestern India and Yunnan of China, the Powassan virus in the United States, Canada, and east Siberia, Alkhurma haemorrhagic fever virus in Saudi Arabia and east Egypt, and Louping-ill virus in the United Kingdom, Ireland, and east Siberia. In some areas, the distribution of the TBEV complex overlaps with that of other viruses, and caution is recommended during serologic diagnosis. The geographic distribution of the TBEV complex appears to be wide and overlap of the TBE virus complex with other viruses was observed in some areas. Knowledge of the geographical distribution of the TBEV complex could help avoid cross-reactivity during the serologic diagnosis of these viruses. Surveillance studies can implement effective control measures according to the distribution pattern of these viruses.
    Matched MeSH terms: Encephalitis Viruses, Tick-Borne/classification; Encephalitis Viruses, Tick-Borne/immunology*; Encephalitis Viruses, Tick-Borne/isolation & purification; Encephalitis Viruses, Tick-Borne/pathogenicity; Encephalitis, Tick-Borne/immunology; Encephalitis, Tick-Borne/epidemiology*
  2. A hospital-based surveillance for Japanese encephalitis in Bali, Indonesia
    Kari K, Liu W, Gautama K, Mammen MP, Clemens JD, Nisalak A, et al.
    BMC Med, 2006;4:8.
    PMID: 16603053
    Japanese encephalitis (JE) is presumed to be endemic throughout Asia, yet only a few cases have been reported in tropical Asian countries such as Indonesia, Malaysia and the Philippines. To estimate the true disease burden due to JE in this region, we conducted a prospective, hospital-based surveillance with a catchment population of 599,120 children less than 12 years of age in Bali, Indonesia, from July 2001 through December 2003.
    Matched MeSH terms: Encephalitis, Japanese/diagnosis; Encephalitis, Japanese/epidemiology*; Encephalitis, Japanese/prevention & control; Japanese Encephalitis Vaccines/therapeutic use
  3. Fulltext Detection of Japanese Encephalitis Virus in Culex Mosquitoes in Singapore
    Yap G, Mailepessov D, Lim XF, Chan S, How CB, Humaidi M, et al.
    Am J Trop Med Hyg, 2020 09;103(3):1234-1240.
    PMID: 32700679 DOI: 10.4269/ajtmh.19-0377
    Mosquito-borne flaviviruses are emerging pathogens of an increasing global public health concern because of their rapid increase in geographical range and the impact of climate change. Japanese encephalitis virus (JEV) and West Nile virus (WNV) are of concern because of the risk of reemergence and introduction by migratory birds. In Singapore, human WNV infection has never been reported and human JEV infection is rare. Four sentinel vector surveillance sites were established in Singapore to understand the potential risk posed by these viruses. Surveillance was carried out from August 2011 to December 2012 at Pulau Ubin, from March 2011 to March 2013 at an Avian Sanctuary (AS), from December 2010 from October 2012 at Murai Farmway, and from December 2010 to December 2013 at a nature reserve. The present study revealed active JEV transmission in Singapore through the detection of JEV genotype II in Culex tritaeniorhynchus collected from an Avian Sanctuary. Culex flavivirus (CxFV), similar to the Quang Binh virus isolated from Cx. tritaeniorhynchus in Vietnam and CxFV-LSFlaviV-A20-09 virus isolated in China, was also detected in Culex spp. (vishnui subgroup). No WNV was detected. This study demonstrates the important role that surveillance plays in public health and strongly suggests the circulation of JEV among wildlife in Singapore, despite the absence of reported human cases. A One Health approach involving surveillance, the collaboration between public health and wildlife managers, and control of mosquito populations remains the key measures in risk mitigation of JEV transmission in the enzootic cycle between birds and mosquitoes.
    Matched MeSH terms: Encephalitis Virus, Japanese/genetics; Encephalitis Virus, Japanese/isolation & purification*; Encephalitis, Japanese/epidemiology*; Encephalitis, Japanese/virology
  4. Fulltext Japanese encephalitis in Malaysia: An overview and timeline
    Kumar K, Arshad SS, Selvarajah GT, Abu J, Toung OP, Abba Y, et al.
    Acta Trop, 2018 Sep;185:219-229.
    PMID: 29856986 DOI: 10.1016/j.actatropica.2018.05.017
    Japanese encephalitis (JE) is a vector-borne zoonotic disease caused by the Japanese encephalitis virus (JEV). It causes encephalitis in human and horses, and may lead to reproductive failure in sows. The first human encephalitis case in Malaya (now Malaysia) was reported during World War II in a British prison in 1942. Later, encephalitis was observed among race horses in Singapore. In 1951, the first JEV was isolated from the brain of an encephalitis patient. The true storyline of JE exposure among humans and animals has not been documented in Malaysia. In some places such as Sarawak, JEV has been isolated from mosquitoes before an outbreak in 1992. JE is an epidemic in Malaysia except Sarawak. There are four major outbreaks reported in Pulau Langkawi (1974), Penang (1988), Perak and Negeri Sembilan (1998-1999), and Sarawak (1992). JE is considered endemic only in Sarawak. Initially, both adults and children were victims of JE in Malaysia, however, according to the current reports; JE infection is only lethal to children in Malaysia. This paper describes a timeline of JE cases (background of each case) from first detection to current status, vaccination programs against JE, diagnostic methods used in hospitals and factors which may contribute to the transmission of JE among humans and animals in Malaysia.
    Matched MeSH terms: Encephalitis, Japanese/epidemiology*; Encephalitis, Japanese/prevention & control; Encephalitis, Japanese/transmission; Japanese Encephalitis Vaccines/immunology
  5. Exotic and emerging viral encephalitides
    Solomon T
    Curr. Opin. Neurol., 2003 Jun;16(3):411-8.
    PMID: 12858080
    The exotic and emerging viral encephalitides are caused by animal or human viruses and characterised by sudden unexpected outbreaks of neurological disease, usually in tropical and sub-tropical regions, but sometimes spreading to temperate areas. Although a wide range of viruses come within this label, as this review highlights, there are common research questions as to the origin and spread of the viruses, the contribution of viral and host factors to the clinical presentations and outcome, and the possibilities for treatment and vaccination.
    Matched MeSH terms: Encephalitis Virus, Japanese/pathogenicity; Encephalitis, Japanese/pathology; Encephalitis, Japanese/therapy; Encephalitis, Japanese/virology; Encephalitis, Viral/pathology*; Encephalitis, Viral/therapy; Encephalitis, Viral/virology*
  6. Origin and evolution of Japanese encephalitis virus in southeast Asia
    Solomon T, Ni H, Beasley DW, Ekkelenkamp M, Cardosa MJ, Barrett AD
    J Virol, 2003 Mar;77(5):3091-8.
    PMID: 12584335
    Since it emerged in Japan in the 1870s, Japanese encephalitis has spread across Asia and has become the most important cause of epidemic encephalitis worldwide. Four genotypes of Japanese encephalitis virus (JEV) are presently recognized (representatives of genotypes I to III have been fully sequenced), but its origin is not known. We have determined the complete nucleotide and amino acid sequence of a genotype IV Indonesian isolate (JKT6468) which represents the oldest lineage, compared it with other fully sequenced genomes, and examined the geographical distribution of all known isolates. JKT6468 was the least similar, with nucleotide divergence ranging from 17.4 to 19.6% and amino acid divergence ranging from 4.7 to 6.5%. It included an unusual series of amino acids at the carboxy terminus of the core protein unlike that seen in other JEV strains. Three signature amino acids in the envelope protein (including E327 Leu-->Thr/Ser on the exposed lateral surface of the putative receptor binding domain) distinguished genotype IV strains from more recent genotypes. Analysis of all 290 JEV isolates for which sequence data are available showed that the Indonesia-Malaysia region has all genotypes of JEV circulating, whereas only more recent genotypes circulate in other areas (P < 0.0001). These results suggest that JEV originated from its ancestral virus in the Indonesia-Malaysia region and evolved there into the different genotypes which then spread across Asia. Our data, together with recent evidence on the origins of other emerging viruses, including dengue virus and Nipah virus, imply that tropical southeast Asia may be an important zone for emerging pathogens.
    Matched MeSH terms: Encephalitis Virus, Japanese/classification; Encephalitis Virus, Japanese/genetics*; Encephalitis Virus, Japanese/pathogenicity; Encephalitis, Japanese/physiopathology; Encephalitis, Japanese/virology*
  7. Fulltext Overview of Japanese encephalitis disease and its prevention. Focus on IC51 vaccine (IXIARO®)
    Amicizia D, Zangrillo F, Lai PL, Iovine M, Panatto D
    J Prev Med Hyg, 2018 Mar;59(1):E99-E107.
    PMID: 29938245 DOI: 10.15167/2421-4248/jpmh2018.59.1.962
    Japanese encephalitis (JE) is a vector-borne disease caused by the Japanese encephalitis virus (JEV). JEV is transmitted by mosquitoes to a wide range of vertebrate hosts, including birds and mammals. Domestic animals, especially pigs, are generally implicated as reservoirs of the virus, while humans are not part of the natural transmission cycle and cannot pass the virus to other hosts. Although JEV infection is very common in endemic areas (many countries in Asia), less than 1% of people affected develop clinical disease, and severe disease affects about 1 case per 250 JEV infections. Although rare, severe disease can be devastating; among the 30,000-50,000 global cases per year, approximately 20-30% of patients die and 30-50% of survivors develop significant neurological sequelae. JE is a significant public health problem for residents in endemic areas and may constitute a substantial risk for travelers to these areas. The epidemiology of JE and its risk to travelers have changed, and continue to evolve. The rapid economic growth of Asian countries has led to a surge in both inbound and outbound travel, making Asia the second most-visited region in the world after Europe, with 279 million international travelers in 2015. The top destination is China, followed by Thailand, Hong Kong, Malaysia and Japan, and the number of travelers is forecast to reach 535 million by 2030 (+ 4.9% per year). Because of the lack of treatment and the infeasibility of eliminating the vector, vaccination is recognized as the most efficacious means of preventing JE. The IC51 vaccine (IXIARO®) is a purified, inactivated, whole virus vaccine against JE. It is safe, well tolerated, efficacious and can be administered to children, adults and the elderly. The vaccination schedule involves administering 2 doses four weeks apart. For adults, a rapid schedule (0-7 days) is available, which could greatly enhance the feasibility of its use. Healthcare workers should inform both short- and long-term travelers of the risk of JE in each period of the year and recommend vaccination. Indeed, it has been shown that short-term travelers are also at risk, not only in rural environments, but also in cities and coastal towns, especially in tourist localities where excursions to country areas are organized.
    Matched MeSH terms: Encephalitis Virus, Japanese/drug effects*; Encephalitis, Japanese/prevention & control*; Japanese Encephalitis Vaccines/administration & dosage*; Japanese Encephalitis Vaccines/adverse effects
  8. Fulltext Nipah virus encephalitis outbreak in Malaysia
    Lam SK, Chua KB
    Clin Infect Dis, 2002 May 1;34 Suppl 2:S48-51.
    PMID: 11938496 DOI: 10.1086/338818
    Emerging infectious diseases involving zoonosis have become important global health problems. The 1998 outbreak of severe febrile encephalitis among pig farmers in Malaysia caused by a newly emergent paramyxovirus, Nipah virus, is a good example. This disease has the potential to spread to other countries through infected animals and can cause considerable economic loss. The clinical presentation includes segmental myoclonus, areflexia, hypertension, and tachycardia, and histologic evidence includes endothelial damage and vasculitis of the brain and other major organs. Magnetic resonance imaging has demonstrated the presence of discrete high-signal-intensity lesions disseminated throughout the brain. Nipah virus causes syncytial formation in Vero cells and is antigenically related to Hendra virus. The Island flying fox (Pteropus hypomelanus; the fruit bat) is a likely reservoir of this virus. The outbreak in Malaysia was controlled through the culling of >1 million pigs.
    Matched MeSH terms: Encephalitis/epidemiology*; Encephalitis/pathology; Encephalitis/physiopathology; Encephalitis/virology
  9. Neurovirulence and host factors in flavivirus encephalitis--evidence from clinical epidemiology
    Solomon T, Winter PM
    Arch. Virol. Suppl., 2004.
    PMID: 15119771
    Japanese encephalitis virus (JEV) and West Nile virus (WNV) provide some of the most important examples of emerging zoonotic viral encephalitides. For these flaviviruses, only a small proportion of those infected develop clinical features, and these may range from a non-specific flu-like illness to a severe fatal meningoencephalitis, often with Parkinsonian features, or a poliomyelitis-like flaccid paralysis. The factors governing the clinical presentations, and outcome of flavivirus infections are poorly understood, but studies have looked at viral virulence determinants and the host immune response. Previous studies on JEV have suggested that the distribution of the four genotypes across Asia may relate to the differing clinical epidemiology (epidemic disease in the north, endemic disease in the south). However, new data based on the complete nucleotide sequence of a virus representing one of the oldest lineages, and phylogenetic analyses of all JEV strains for which genetic data are available, suggest that the distribution is best explained in terms of the virus' origin in the Indonesia-Malaysia region (where all genotypes have been found), and the spread of the more recent genotypes to new geographical areas. Clinical studies have shown that innate immunity, as manifested by interferon alpha levels, is important in JEV and other flaviviruses, but treatment with interferon alpha did not improve the outcome. A failure of the humoral immune response, is associated with death from encephalitis caused by JEV and WNV. Cellular immunity has been less well characterized, but CD8+ and CD4+ T cells are thought to be important.
    Matched MeSH terms: Encephalitis Virus, Japanese/pathogenicity*; Encephalitis, Japanese/epidemiology*; Encephalitis, Japanese/transmission
  10. The appearance of a second genotype of Japanese encephalitis virus in the Australasian region
    Pyke AT, Williams DT, Nisbet DJ, van den Hurk AF, Taylor CT, Johansen CA, et al.
    Am J Trop Med Hyg, 2001 Dec;65(6):747-53.
    PMID: 11791969
    In mid-January 2000, the reappearance of Japanese encephalitis (JE) virus activity in the Australasian region was first demonstrated by the isolation of JE virus from 3 sentinel pigs on Badu Island in the Torres Strait. Further evidence of JE virus activity was revealed through the isolation of JE virus from Culex gelidus mosquitoes collected on Badu Island and the detection of specific JE virus neutralizing antibodies in 3 pigs from Saint Pauls community on Moa Island. Nucleotide sequencing and phylogenetic analyses of the premembrane and envelope genes were performed which showed that both the pig and mosquito JE virus isolates (TS00 and TS4152, respectively) clustered in genotype I, along with northern Thai, Cambodian, and Korean isolates. All previous Australasian JE virus isolates belong to genotype II, along with Malaysian and Indonesian isolates. Therefore, for the first time, the appearance and transmission of a second genotype of JE virus in the Australasian region has been demonstrated.
    Matched MeSH terms: Encephalitis Virus, Japanese/genetics*; Encephalitis Virus, Japanese/isolation & purification; Encephalitis, Japanese/epidemiology*
  11. Outbreak of Japanese encephalitis hits Malaysia
    Easton A
    BMJ, 1999 Apr 03;318(7188):893.
    PMID: 10102839 DOI: 10.1136/bmj.318.7188.893a
    Matched MeSH terms: Encephalitis, Japanese/epidemiology*; Encephalitis, Japanese/prevention & control
  12. High mortality in Nipah encephalitis is associated with presence of virus in cerebrospinal fluid
    Chua KB, Lam SK, Tan CT, Hooi PS, Goh KJ, Chew NK, et al.
    Ann Neurol, 2000 Nov;48(5):802-5.
    PMID: 11079547
    During the outbreak of Nipah virus encephalitis in Malaysia, stored cerebrospinal fluid (CSF) samples from 84 patients (27 fatal and 57 nonfatal cases) were cultured for the virus. The virus was isolated from 17 fatal cases and 1 nonfatal case. There were significant associations between CSF virus isolation and mortality as well as clinical features associated with poor prognosis. In addition, there was a positive linear correlation of CSF virus isolation with age. There was no significant association between CSF virus isolation and the character of the CSF, presence of Nipah-specific antibody in the serum or CSF, duration of illness before collection of samples, or sex or ethnicity of the patients. This study suggests that high viral replication in the central nervous system may be an important factor for high mortality.
    Matched MeSH terms: Encephalitis/cerebrospinal fluid*; Encephalitis/virology*
  13. Studies on arbovirus epidemiology associated with established and developing rice culture. Introduction
    Smith CE
    Trans R Soc Trop Med Hyg, 1970;64(4):481-2.
    PMID: 4320902
    Matched MeSH terms: Encephalitis, Japanese/epidemiology*; Encephalitis, Japanese/veterinary
  14. Mild encephalitis/encephalopathy with reversible splenial lesion (MERS) due to dengue virus
    Fong CY, Khine MM, Peter AB, Lim WK, Rozalli FI, Rahmat K
    J Clin Neurosci, 2017 Feb;36:73-75.
    PMID: 27887978 DOI: 10.1016/j.jocn.2016.10.050
    A 14-year-old girl presented with encephalopathy, delirium and ophthalmoplegia following a 3day history of high-grade fever. Brain MRI on day 6 of illness showed diffusion restricted ovoid lesion in the splenium of corpus callosum. Dengue virus encephalitis was diagnosed with positive PCR for dengue virus type-2 in both serum and cerebrospinal fluid. She made a complete recovery from day 10 of illness. Repeat brain MRI on day 12 of illness showed resolution of the splenial lesion. Serial diffusion tensor imaging (DTI) showed normal fractional anisotropy values on resolution of splenial lesion indicating that MERS was likely due to transient interstitial oedema with preservation of white matter tracts. This is the first reported case of MERS following dengue virus infection. It highlights the usefulness of performing serial DTI in understanding the underlying pathogenesis of MERS. Our case report widens the neurological manifestations associated with dengue infection and reiterates that patients with MERS should be managed supportively as the splenial white matter tracts are reversibly involved in MERS.
    Matched MeSH terms: Encephalitis, Viral/etiology; Encephalitis, Viral/pathology
  15. Fulltext Emerging epidemic viral encephalitides with a special focus on henipaviruses
    Wong KT
    Acta Neuropathol, 2010 Sep;120(3):317-25.
    PMID: 20652579 DOI: 10.1007/s00401-010-0720-z
    In the last few decades, there is an increasing emergence and re-emergence of viruses, such as West Nile virus, Enterovirus 71 and henipaviruses that cause epidemic viral encephalitis and other central nervous system (CNS) manifestations. The mortality and morbidity associated with these outbreaks are significant and frequently severe. While aspects of epidemiology, basic virology, etc., may be known, the pathology and pathogenesis are often less so, partly due to a lack of interest among pathologists or because many of these infections are considered "third world" diseases. In the study of epidemic viral encephalitis, the pathologist's role in unravelling the pathology and pathogenesis is critical. The novel henipavirus infection is a good example. The newly created genus Henipavirus within the family Paramyxoviridae consists of two viruses, viz., Hendra virus and Nipah virus. These two viruses emerged in Australia and Asia, respectively, to cause severe encephalitides in humans and animals. Studies show that the pathological features of the acute encephalitis caused by henipaviruses are similar and a unique dual pathogenetic mechanism of vasculitis-induced microinfarction and parenchymal cell infection in the CNS (mainly neurons) and other organs causes severe tissue damage. Both viruses can cause relapsing encephalitis months and years after the acute infection due to a true recurrent infection as evidenced by the presence of virus in infected cells. Future emerging viral encephalitides will no doubt continue to pose considerable challenges to the neuropathologist, and as the West Nile virus outbreak demonstrates, even economically advanced nations are not spared.
    Matched MeSH terms: Encephalitis, Viral/epidemiology*; Encephalitis, Viral/pathology*
  16. Fulltext The involvement of microtubules and actin during the infection of Japanese encephalitis virus in neuroblastoma cell line, IMR32
    Henry Sum MS
    Biomed Res Int, 2015;2015:695283.
    PMID: 25705678 DOI: 10.1155/2015/695283
    The role of the cytoskeleton, actin, and microtubules were examined during the process of Japanese encephalitis (JEV) infection in a human neuroblastoma cell line, IMR32. Cytochalasin D and nocodazole were used to depolymerise the cellular actin and microtubules, respectively, in order to study the effect of JEV infection in the cell. This study shows that depolymerisation of the actin cytoskeleton at early process of infection inhibits JEV infection in the cell; however infection was not inhibited when depolymerisation occurred at the later stage of infection. The microtubules, on the other hand, are required at 2 points in infection. The antigen production in the cells was inhibited when the infected cells were treated at time up to 2 hours after inoculation and there was no significant effect at later times, while the viable virus released continued to be affected until 10 hours after inoculation. In conclusion, infection of JEV in IMR32 cells required actin to facilitate early process in infection and the microtubular network is utilised as the transport system to the virus replication site and the release of mature virus.
    Matched MeSH terms: Encephalitis Virus, Japanese/genetics; Encephalitis Virus, Japanese/pathogenicity*; Encephalitis, Japanese/genetics; Encephalitis, Japanese/virology*
  17. Fulltext Antiviral activity of baicalein and quercetin against the Japanese encephalitis virus
    Johari J, Kianmehr A, Mustafa MR, Abubakar S, Zandi K
    Int J Mol Sci, 2012;13(12):16785-95.
    PMID: 23222683 DOI: 10.3390/ijms131216785
    Japanese encephalitis (JE), a mosquito-borne viral disease, is endemic to the entire east and southeast Asia, and some other parts of the world. Currently, there is no effective therapeutic available for JE; therefore, finding the effective antiviral agent against JEV replication is crucial. In the present study, the in vitro antiviral activity of baicalein and quercetin, two purportedly antiviral bioflavonoids, was evaluated against Japanese encephalitis virus (JEV) replication in Vero cells. Anti-JEV activities of these compounds were examined on different stages of JEV replication cycle. The effects of the compounds on virus replication were determined by foci forming unit reduction assay (FFURA) and quantitative RT-PCR. Baicalein showed potent antiviral activity with IC(50) = 14.28 µg/mL when it was introduced to the Vero cells after adsorption of JEV. Quercetin exhibited weak anti-JEV effects with IC(50) = 212.1 µg/mL when the JEV infected cells were treated with the compound after virus adsorption. However, baicalein exhibited significant effect against JEV adsorption with IC(50) = 7.27 µg/mL while quercetin did not show any anti-adsorption activity. Baicalein also exhibited direct extracellular virucidal activity on JEV with IC(50) = 3.44 µg/mL. However, results of quantitative RT-PCR experiments confirmed the findings from FFURA. This study demonstrated that baicalein should be considered as an appropriate candidate for further investigations, such as the study of molecular and cellular mechanism(s) of action and in vivo evaluation for the development of an effective antiviral compound against Japanese encephalitis virus.
    Matched MeSH terms: Encephalitis Virus, Japanese/drug effects*; Encephalitis Virus, Japanese/physiology; Encephalitis, Japanese/prevention & control; Encephalitis, Japanese/virology
  18. Fulltext The effect of vaccination coverage and climate on Japanese encephalitis in Sarawak, Malaysia
    Impoinvil DE, Ooi MH, Diggle PJ, Caminade C, Cardosa MJ, Morse AP, et al.
    PLoS Negl Trop Dis, 2013;7(8):e2334.
    PMID: 23951373 DOI: 10.1371/journal.pntd.0002334
    BACKGROUND: Japanese encephalitis (JE) is the leading cause of viral encephalitis across Asia with approximately 70,000 cases a year and 10,000 to 15,000 deaths. Because JE incidence varies widely over time, partly due to inter-annual climate variability effects on mosquito vector abundance, it becomes more complex to assess the effects of a vaccination programme since more or less climatically favourable years could also contribute to a change in incidence post-vaccination. Therefore, the objective of this study was to quantify vaccination effect on confirmed Japanese encephalitis (JE) cases in Sarawak, Malaysia after controlling for climate variability to better understand temporal dynamics of JE virus transmission and control.

    METHODOLOGY/PRINCIPAL FINDINGS: Monthly data on serologically confirmed JE cases were acquired from Sibu Hospital in Sarawak from 1997 to 2006. JE vaccine coverage (non-vaccine years vs. vaccine years) and meteorological predictor variables, including temperature, rainfall and the Southern Oscillation index (SOI) were tested for their association with JE cases using Poisson time series analysis and controlling for seasonality and long-term trend. Over the 10-years surveillance period, 133 confirmed JE cases were identified. There was an estimated 61% reduction in JE risk after the introduction of vaccination, when no account is taken of the effects of climate. This reduction is only approximately 45% when the effects of inter-annual variability in climate are controlled for in the model. The Poisson model indicated that rainfall (lag 1-month), minimum temperature (lag 6-months) and SOI (lag 6-months) were positively associated with JE cases.

    CONCLUSIONS/SIGNIFICANCE: This study provides the first improved estimate of JE reduction through vaccination by taking account of climate inter-annual variability. Our analysis confirms that vaccination has substantially reduced JE risk in Sarawak but this benefit may be overestimated if climate effects are ignored.

    Matched MeSH terms: Encephalitis, Japanese/epidemiology*; Encephalitis, Japanese/prevention & control*; Japanese Encephalitis Vaccines/administration & dosage*; Japanese Encephalitis Vaccines/immunology*
  19. Encephalitis in racehorses in Malaya
    HALE JH, WITHERINGTON DH
    J Comp Pathol, 1953 Jul;63(3):195-8.
    PMID: 13084794
    Matched MeSH terms: Encephalitis*
  20. Methods of sampling population of the Japanese encephalitis vector mosquitoes. A preliminary report
    Ree HI, Chen YK, Chow CY
    Med J Malaya, 1969 Jun;23(4):293-5.
    PMID: 4310350
    Matched MeSH terms: Encephalitis, Japanese/epidemiology*
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