Dengue continues to be a major health threat to Malaysia a century after its first reported outbreak in 1902. Examination of the available outbreak data suggested that a major DF/DHF outbreak occurred in Malaysia in a cyclical pattern of approximately every 8 years. All four dengue virus serotypes are found co-circulating in Malaysia, but after the first and only major outbreak involving DEN-4 in 1960's, only DEN-1, DEN-2 and DEN-3 were associated with DF/DHF outbreaks. It is argued that perhaps the spread of the later dengue virus serotypes followed the pattern of spread of the mosquito vector Aedes aegypti, whereas the former was associated with Aedes albopictus, the outdoor and rural area dwelling mosquito. Estimating from the trend and pattern of dengue and the associated dengue virus serotypes, unless there is a major breakthrough in dengue vaccine development, it is likely that dengue outbreaks will continue to occur in Malaysia throughout the 21st century.
Malaysia ; Dengue ; Pattern ; Dengue Virus ; increasing incidence

Phylogenetic analysis of Nipah virus isolates from Malaysia, Bangladesh and Cambodia suggested the presence of at least two different clusters of NiV strains. Based on the major glycoprotein (G) gene, the Nipah virus-Tambun isolate clustered with Nipah virus isolates from Cambodia and Bangladesh, whereas the remaining isolates from Malaysia clustered in a separate cluster. Sequence heterogeneity among the Nipah virus isolates from Malaysia was noted but the overall genomic sequence divergence value was small, suggesting a possible recent introduction of the virus. Nipah virus replicated well in porcine stable kidney cells and human lung fibroblast cells. Human monocytes, on the other hand were infected with Nipah virus but the cells did not support productive infection. Similarly, infection of human neuronal cells did not result in release of high infectious virus yield. The monocytes can serve to disseminate Nipah virus from site of infection including across the blood-brain barrier. And in the brain, Nipah virus is probably spread through cell-to-cell spread mechanism.

The effects of Enterovirus 71 (HEV71) infection on African green monkey kidney cells (Vero) were investigated. It was found that the infected cells showed progressive cellular morphological changes characteristic in apoptotic cells within 10 hours post-infection. The number of apoptotic cells correlated significantly with the number of HEV71 antigen positive cells when cells were labeled using terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) and stained for HEV71 antigen. Approximately 11, 26, 45 and 50% of the infected cells were apoptotic at 12, 24, 48 and 72 hours post-infection, respectively. Internucleosomal DNA fragmentation, characteristic in the late stage of apoptosis was noted beginning on day 2 post-infection. The DNA fragmentation, however, was absent in cells treated with the heat- and ultraviolet light-inactivated virus inocula. These results demonstrate the capacity of HEV71 to induce apoptosis in the infected cells. The induction, however, requires high level of HEV71 infectivity and the presence of live virus particles, suggesting the need for the presence of specific viral proteins for apoptosis to occur.
Infection as complication of medical care ; Apoptosis ; seconds ; Enterovirus ; Hour

At least three major antigenic dengue 2 virus proteins were recognized by pooled dengue fever patients' sera in infected Aedes albopictus (C6/36) mosquito cells. Dengue virus envelope (E), premembrane (PrM) and non-structural protein 1 (NS 1) dimer were detected beginning on day 3 postinfection in both the cell membrane and cytosolic fractions. Using the patients' sera, the presence of antigenic intermediate core protein (C)-PrM and NS1-non-structural protein 2a (NS2a) in the cytoplasmic fraction of dengue 2 virus infected cells was revealed. The presence of a approximately 92 and approximately 84 kDa NS 1 dimer in the membrane (NS 1m) and cytosolic (NS 1c) fractions of C6/36 cells, respectively, was also recognized. Using individual patient's serum, it was further confirmed that all patients' sera contained antibodies that specifically recognized E, NS 1 and PrM present in the dengue 2 virus-infected cell membrane fractions, suggesting that these glycosylated virus proteins were the main antigenic proteins recognized in vivo. Detection of dengue 2 virus C antibody in some patients further suggested that C could be antigenic if presented in vivo.
Dengue ; seconds ; Viral Proteins ; Proteins ; Carbon ion

In the last decade, Malaysia has experienced several hand, foot and mouth disease (HFMD) epidemics, complicated by fatalities due to severe neurological involvement. Enterovirus 71 (EV-71) has been implicated as the major causative agent for these epidemics. EV-71 infection is a global public health problem with pandemic potential. In many parts of Asia-Pacifi c, the virus has emerged as one of the most deadly virus infections amongst young children. The virus is highly transmissible through faecaloral route and respiratory droplets. A recent rise in neurological complications and deaths suggests that the viruses currently circulating may be more virulent. The major risk factor associated with more severe EV-71 infection is young age and poor cellular immunity. Rapid laboratory diagnosis and molecular surveillance is important to closely monitor the emergence of new EV-71 subgenotypes. Since vaccine and anti-virals for EV-71 are not available, control and prevention strategies remain the only ways to combat the infection.

Objective: To identify the unusual breeding sites of two dengue vectors, i.e. Aedes albopictus (Ae. albopictus) and Aedes aegypti (Ae. aegypti). Methods: During the second half of 2010, we performed an occasional survey in rural (Teluk Tempoyak) and urban (Gelugor) areas of Penang Island, Malaysia, to identify cryptic breeding sites. Results: In the rural area, we found heterogeneous immature stages of Ae. albopictus in the water bowl of an encaged bird. We also observed Ae. aegypti eggs deposited in the flush tank of a toilet in the urban area. Conclusions:It can be concluded that both breeding patterns can increase contact with hosts (humans and birds) and presumably population densities of Ae. albopictus and Ae. aegypti, thereby potentially boosting the risks for spread and transmission of arboviral diseases.

OBJECTIVE: To conduct an external quality assessment (EQA) of dengue and chikungunya diagnostics among national-level public health laboratories in the Asia Pacific region following the first round of EQA for dengue diagnostics in 2013. METHODS: Twenty-four national-level public health laboratories performed routine diagnostic assays on a proficiency testing panel consisting of two modules. Module A contained serum samples spiked with cultured dengue virus (DENV) or chikungunya virus (CHIKV) for the detection of nucleic acid and DENV non-structural protein 1 (NS1) antigen. Module B contained human serum samples for the detection of anti-DENV antibodies. RESULTS: Among 20 laboratories testing Module A, 17 (85%) correctly detected DENV RNA by reverse transcription polymerase chain reaction (RT-PCR), 18 (90%) correctly determined serotype and 19 (95%) correctly identified CHIKV by RT-PCR. Ten of 15 (66.7%) laboratories performing NS1 antigen assays obtained the correct results. In Module B, 18/23 (78.3%) and 20/20 (100%) of laboratories correctly detected anti-DENV IgM and IgG, respectively. Detection of acute/recent DENV infection by both molecular (RT-PCR) and serological methods (IgM) was available in 19/24 (79.2%) participating laboratories. DISCUSSION: Accurate laboratory testing is a critical component of dengue and chikungunya surveillance and control. This second round of EQA reveals good proficiency in molecular and serological diagnostics of these diseases in the Asia Pacific region. Further comprehensive diagnostic testing, including testing for Zika virus, should comprise future iterations of the EQA.

Objective:Accurate laboratory testing is a critical component of dengue surveillance and control. The objective of this programme was to assess dengue diagnostic proficiency among national-level public health laboratories in the World Health Organization (WHO) Western Pacific Region.Methods:Nineteen national-level public health laboratories performed routine dengue diagnostic assays on a proficiency testing panel consisting of two modules: one containing commercial serum samples spiked with cultured dengue viruses for the detection of nucleic acid and non-structural protein 1 (NS1) (Module A) and one containing human serum samples for the detection of anti-dengue virus antibodies (Module B). A review of logistics arrangements was also conducted.Results:All 16 laboratories testing Module A performed reverse transcriptase polymerase chain reaction (RT–PCR) for both RNA and serotype detection. Of these, 15 had correct results for RNA detection and all 16 correctly serotyped the viruses. All nine laboratories performing NS1 antigen detection obtained the correct results. Sixteen of the 18 laboratories using IgM assays in Module B obtained the correct results as did the 13 laboratories that performed IgG assays. Detection of ongoing/recent dengue virus infection by both molecular (RT–PCR) and serological methods (IgM) was available in 15/19 participating laboratories.Discussion:This first round of external quality assessment of dengue diagnostics was successfully conducted in national-level public health laboratories in the WHO Western Pacific Region, revealing good proficiency in both molecular and serological testing. Further comprehensive diagnostic testing for dengue virus and other priority pathogens in the Region will be assessed during future rounds.

Objective: To investigate the involvement of Ca2+ in dengue virus (DENV)-infected human umbilical vein endothelial cells (HUVECs) and the disruption of endothelial integrity. Methods: HUVECs were infected with DENV-2 in the presence of intracellular Ca2+ or endoplasmic reticulum Ca2+ chelators. Virus infectivity was measured by focus-forming assay and quantitative RT-PCR. Intracellular Ca2+ was measured using Fluo-4-AM dye. VE-cadherin and focal adhesion kinase (FAK) expressions were investigated by immunofluorescence and immunoblotting assays, respectively. Results: DENV infection increased intracellular cytosolic Ca2+ levels and caused disassembly of the adherens junction protein, VEcadherin as evidenced by decreased VE-cadherin expression at the periphery of DENV-2 infected HUVECs. Depletion of intracellular Ca2+ stores, particularly those of the endoplasmic reticulum Ca2+, significantly decreased DENV yield in HUVECs. Decreased virus yield following the depletion of intracellular Ca2+ was caused by the inhibition of viral entry into HUVECs and not the inhibition of viral binding or attachment. DENV-2 infection also resulted in Ca2+- dependent activation of FAK. Conclusions: Intracellular Ca2+ is required for the early phases of DENV infection in endothelial cells. Increased cytosolic Ca2+ levels in endothelial cells during DENV infection activated FAK, disrupted adherens junctions and compromised barrier integrity. Thus, Ca2+ plays an important role in DENV infection in endothelial cells.