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Fulltext A decade of Japanese encephalitis surveillance in Sarawak, Malaysia: 1997-2006

Wong SC, Ooi MH, Abdullah AR, Wong SY, Krishnan S, Tio PH, et al.

Trop Med Int Health, 2008 Jan;13(1):52-5.
PMID: 18291002 DOI: 10.1111/j.1365-3156.2007.01967.x

Japanese encephalitis virus (JEV) is an important encephalitis virus in Asia, but there are few data on Malaysia. A hospital-based surveillance system for Japanese encephalitis (JE) has been in operation in Sarawak, Malaysia, for the last 10 years. JEV is endemic in Sarawak, with cases occurring throughout the year and a seasonal peak in the last quarter (one-way anova, P < 0.0001). Ninety-two per cent of 133 cases were children aged 12 years or younger; the introduction of JE vaccination in July 2001 reduced the number of JE cases (84 in the four seasons prior to vs. 49 in the six seasons after, McNemar's test, P = 0.0001). After implementation of the programme, the mean age of infected children increased from 6.3 to 8.0 years (Student's t-test, P = 0.0037), suggesting the need for a catch-up programme.

Matched MeSH terms: Encephalitis, Japanese/epidemiology*
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/epidemiology*
A review of Japanese-B virus encephalitis in Malaysia

Sinniah M

Southeast Asian J. Trop. Med. Public Health, 1989 Dec;20(4):581-5.
PMID: 2561714

JE is neither classified as an entity in the Malaysian Medical records system nor is it a notifiable disease but is grouped under the broad umbrella of viral encephalitis. There is no centralised program by the Ministry of Health specially for JE surveillance and control. JE is endemic, occurs sporadically throughout the country all year round. Asymptomatic inapparent infections have been found to be more frequent than acute clinical encephalitis cases, judging from results of previous serosurveys (Pond et al., 1954). JE vaccination has never been tried in Malaysia. In a relative sense, JEV infection unlike dengue virus infection, does not appear to be much of a problem in Malaysia. Perhaps, the laboratory confirmed cases represent only a small proportion of the total hospitalised cases that actually occurred. The reasons may be that these cases could not be confirmed by laboratory tests due to improper timing or failure to obtain the second serum specimen, or failure to perform lumbar puncture on patient's refusal. Attempts to improve the case detection rate of JE in Malaysia should be made namely, by increasing clinical index of suspicion, instituting better specimen collection procedures and by adopting rapid diagnostic tests.

Matched MeSH terms: Encephalitis, Japanese/epidemiology*
Fulltext A serological study of Japanese encephalitis virus infections in northern Peninsular Malaysia

Cardosa MJ, Choo BH, Zuraini I

Southeast Asian J. Trop. Med. Public Health, 1991 Sep;22(3):341-6.
PMID: 1667957

This study describes the status of viral encephalitis in Perak, Malaysia during the year 1990. In addition, 14 cases selected from Penang and Perak during the years 1989 and 1990 are presented, with data showing titers of neutralizing antibodies against Japanese encephalitis virus (JEV) and dengue 2 virus, titers of antibodies against JEV and dengue virus antigens as determined by DEIA, and a comparison of these with the presence of IgM to JEV and dengue virus. These data show that there probably is far more viral encephalitis due to JEV in Malaysia than the national figures reflect.

Matched MeSH terms: Encephalitis, Japanese/epidemiology*
A serological survey of antibodies to Japanese B encephalitis virus among horses in Malaya

HALE JH, WITHERINGTON DH

Ann Trop Med Parasitol, 1954 Mar;48(1):15-20.
PMID: 13149114
Matched MeSH terms: Encephalitis, Japanese/epidemiology*
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, Japanese/epidemiology*
Fulltext Emergence of Japanese encephalitis virus genotype V in the Republic of Korea

Takhampunya R, Kim HC, Tippayachai B, Kengluecha A, Klein TA, Lee WJ, et al.

Virol J, 2011;8:449.
PMID: 21943222 DOI: 10.1186/1743-422X-8-449

Japanese encephalitis virus (JEV) genotype V reemerged in Asia (China) in 2009 after a 57-year hiatus from the continent, thereby emphasizing a need to increase regional surveillance efforts. Genotypic characterization was performed on 19 JEV-positive mosquito pools (18 pools of Culex tritaeniorhynchus and 1 pool of Cx. bitaeniorhynchus) from a total of 64 positive pools collected from geographically different locations throughout the Republic of Korea (ROK) during 2008 and 2010.

Matched MeSH terms: Encephalitis, Japanese/epidemiology
Fulltext Genetic diversity of Japanese encephalitis virus isolates obtained from the Indonesian archipelago between 1974 and 1987

Schuh AJ, Guzman H, Tesh RB, Barrett AD

Vector Borne Zoonotic Dis, 2013 Jul;13(7):479-88.
PMID: 23590316 DOI: 10.1089/vbz.2011.0870

Five genotypes (GI-V) of Japanese encephalitis virus (JEV) have been identified, all of which have distinct geographical distributions and epidemiologies. It is thought that JEV originated in the Indonesia-Malaysia region from an ancestral virus. From that ancestral virus GV diverged, followed by GIV, GIII, GII, and GI. Genotype IV appears to be confined to the Indonesia-Malaysia region, as GIV has been isolated in Indonesia from mosquitoes only, while GV has been isolated on three occasions only from a human in Malaysia and mosquitoes in China and South Korea. In contrast, GI-III viruses have been isolated throughout Asia and Australasia from a variety of hosts. Prior to this study only 13 JEV isolates collected from the Indonesian archipelago had been studied genetically. Therefore the sequences of the envelope (E) gene of 24 additional Indonesian JEV isolates, collected throughout the archipelago between 1974 and 1987, were determined and a series of molecular adaptation analyses were performed. Phylogenetic analysis indicated that over a 14-year time span three genotypes of JEV circulated throughout Indonesia, and a statistically significant association between the year of virus collection and genotype was revealed: isolates collected between 1974 and 1980 belonged to GII, isolates collected between 1980 and 1981 belonged to GIV, and isolates collected in 1987 belonged to GIII. Interestingly, three of the GII Indonesian isolates grouped with an isolate that was collected during the JE outbreak that occurred in Australia in 1995, two of the GIII Indonesian isolates were closely related to a Japanese isolate collected 40 years previously, and two Javanese GIV isolates possessed six amino acid substitutions within the E protein when compared to a previously sequenced GIV isolate collected in Flores. Several amino acids within the E protein of the Indonesian isolates were found to be under directional evolution and/or co-evolution. Conceivably, the tropical climate of the Indonesia/Malaysia region, together with its plethora of distinct fauna and flora, may have driven the emergence and evolution of JEV. This is consistent with the extensive genetic diversity seen among the JEV isolates observed in this study, and further substantiates the hypothesis that JEV originated in the Indonesia-Malaysia region.

Matched MeSH terms: Encephalitis, Japanese/epidemiology*
Fulltext Investigation of a suspected outbreak of Japanese encephalitis in Pulau Langkawi

Fang R, Hsu DR, Lim TW

Malays J Pathol, 1980 Aug;3:23-30.
PMID: 6312203
Matched MeSH terms: Encephalitis, Japanese/epidemiology*
Fulltext Japanese Encephalitis in Assam, India: Need to Increase Healthcare Workers' Understanding to Improve Health Care

Ahmad A, Khan MU, Gogoi LJ, Kalita M, Sikdar AP, Pandey S, et al.

PLoS One, 2015;10(8):e0135767.
PMID: 26296212 DOI: 10.1371/journal.pone.0135767

INTRODUCTION: Japanese encephalitis (JE) is a major cause of high morbidity and mortality in several states across India. However, in 2014, a sharp rise was observed in the number of cases of JE in north-eastern Assam state, and 51% of the total cases of JE in India were reported from the Assam in the same year. In this regard, a study was conducted to evaluate the knowledge and attitudes of healthcare workers in Darrang, a district of Assam highly affected by JE.
METHODS: A cross sectional study was conducted for 2 months among HCWs in the major district hospital of Darrang, Assam. A pre-tested, self-administered questionnaire was used to collect data from the participants. Convenience sampling approach was used to collect data from different departments of the hospitals. Descriptive and logistic regression analyses were used to express the results.
RESULTS: The knowledge of HCWs regarding JE was poor with a mean knowledge score of 11.02±2.39 (out of 17), while their attitudes were positive with a mean attitudes score of 43.16± 2.47 (ranging from 13 to 52). Overall, 40.4% and 74.3% of participants demonstrated good knowledge and positive attitudes respectively. Cut-off score for good knowledge and positive attitudes toward JE was set as ≥12 and >40 respectively. Older participants (40-49 years) and experienced workers (>10 years) were significantly associated with good knowledge as compared to their referent group (p<0.05), while knowledge of nurses and other orderlies were significantly lower than physicians (p<0.01). Similar factors were associated with the positive attitudes of the participants with the exception of experience. Television was the major source of information regarding JE reported by HCWs (79%).
CONCLUSION: Although the knowledge was not optimized, HCWs exhibited positive attitudes towards JE. Future research is required to design, implement and evaluate interventions to improve the knowledge of JE among HCWs.

Matched MeSH terms: Encephalitis, Japanese/epidemiology
Japanese encephalitis in Malaya. I. Isolation of virus and serologic evidence of human and equine infections

PATERSON PY, LEY HL, WISSEMAN CL, POND WL, SMADEL JE, DIERCKS FH, et al.

Am J Hyg, 1952 Nov;56(3):320-33.
PMID: 12996500
Matched MeSH terms: Encephalitis, Japanese/epidemiology*
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*
Japanese encephalitis in Sarawak: studies on adult mosquito populations

Hill MN

Trans R Soc Trop Med Hyg, 1970;64(4):489-96.
PMID: 4394984
Matched MeSH terms: Encephalitis, Japanese/epidemiology*
Japanese encephalitis in Sarawak: studies on juvenile mosquito populations

Heathcote OH

Trans R Soc Trop Med Hyg, 1970;64(4):483-8.
PMID: 4394983
Matched MeSH terms: Encephalitis, Japanese/epidemiology*
Japanese encephalitis in Sarawak: studies on mosquito behaviour in a Land Dayak village

Bendell PJ

Trans R Soc Trop Med Hyg, 1970;64(4):497-502.
PMID: 4394985
Matched MeSH terms: Encephalitis, Japanese/epidemiology*
Japanese encephalitis in Sarawak: virus isolation and serology in a Land Dyak village

Simpson DI, Bowen ET, Platt GS, Way H, Smith CE, Peto S, et al.

Trans R Soc Trop Med Hyg, 1970;64(4):503-10.
PMID: 4394986
Matched MeSH terms: Encephalitis, Japanese/epidemiology*
Fulltext Japanese encephalitis virus is an important cause of encephalitis among children in Penang

Cardosa MJ, Hooi TP, Kaur P

Southeast Asian J. Trop. Med. Public Health, 1995 Jun;26(2):272-5.
PMID: 8629059

This study was carried out to determine if Japanese encephalitis virus is an important causative agent of viral encephalitis among pediatric admissions in Penang, Malaysia. 195 children with CNS symptoms and 482 children with non-specific febrile illness admitted into the Pediatric Ward of Penang Hospital during a 16 month period were entered into the study. The presence in serum of cerebrospinal fluid (csf) of Japanese encephalitis virus (JEV) specific IgM was determined by an IgM capture ELISA and cytomegalovirus (CMV) specific IgM was determined using a commercially available kit (Behringwerke AG). It was determined that 5 of 13 children with a discharge diagnosis of viral encephalitis had JEV specific IgM in csf, indicating that 38.5% of the viral encephalitis cases was due to JEV. One of the non-JEV cases was found to have mumps virus specific IgM in csf, while no etiology was determined for the other cases. It was also determined that 4 of the 195 (2.1%) cases with CNS symptoms had IgM to CMV, suggesting CMV may be an agent of encephalopathy in children in Penang. Other viruses found to be associated with CNS symptoms in children admitted into our study were measles and herpes simplex virus. A viral etiology was confirmed for 13 or the 195 cases (6.7%). We also screened 482 non-specific febrile cases for IgM to JEV and to dengue viruses and found that 2 (0.4%) had IgM specific for JEV and 9 (1.9%) had IgM specific for dengue virus.

Matched MeSH terms: Encephalitis, Japanese/epidemiology
Japanese type B encephalitis in Malaya

HALE JH, LIM KA, CHEE PH

Ann Trop Med Parasitol, 1952 Nov;46(3):220-6.
PMID: 13008352
Matched MeSH terms: Encephalitis, Japanese/epidemiology*
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*
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, Japanese/epidemiology*

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