Dengue virus type 1 clade replacement in recurring homotypic outbreaks

BACKGROUND: Recurring dengue outbreaks occur in cyclical pattern in most endemic countries. The recurrences of dengue virus (DENV) infection predispose the population to increased risk of contracting the severe forms of dengue. Understanding the DENV evolutionary mechanism underlying the recurring dengue outbreaks has important implications for epidemic prediction and disease control. RESULTS: We used a set of viral envelope (E) gene to reconstruct the phylogeny of DENV-1 isolated between the periods of 1987–2011 in Malaysia. Phylogenetic analysis of DENV-1 E gene revealed that genotype I virus clade replacements were associated with the cyclical pattern of major DENV-1 outbreaks in Malaysia. A total of 9 non-conservative amino acid substitutions in the DENV-1 E gene consensus were identified; 4 in domain I, 3 in domain II and 2 in domain III. Selection pressure analyses did not reveal any positively selected codon site within the full length E gene sequences (1485 nt, 495 codons). A total of 183 (mean dN/dS = 0.0413) negatively selected sites were found within the Malaysian isolates; neither positive nor negative selection was noted for the remaining 312 codons. All the viruses were cross-neutralized by the respective patient sera suggesting no strong support for immunological advantage of any of the amino acid substitutions. CONCLUSION: DENV-1 clade replacement is associated with recurrences of major DENV-1 outbreaks in Malaysia. Our findings are consistent with those of other studies that the DENV-1 clade replacement is a stochastic event independent of positive selection

Isolation of Ancestral Sylvatic Dengue Virus Type 1, Malaysia

Ancestral sylvatic dengue virus type 1, which was isolated from a monkey in 1972, was isolated from a patient with dengue fever in Malaysia. The virus is neutralized by serum of patients with endemic DENV-1 infection. Rare isolation of this virus suggests a limited spillover infection from an otherwise restricted sylvatic cycle

Possible Factors Influencing the Seroprevalence of Dengue among Residents of the Forest Fringe Areas of Peninsular Malaysia

Dengue is an endemic mosquito-borne viral disease prevalent in many urban areas of the tropic, especially the Southeast Asia. Its presence among the indigenous population of Peninsular Malaysia (Orang Asli), however, has not been well described. -epresent study was performed to investigate the seroprevalence of dengue among the Orang Asli (OA) residing at the forest fringe areas of Peninsular Malaysia and determine the factors that could affect the transmission of dengue among the OA. Eight OA communities consisting of 491 individuals were recruited. From the study, at least 17% of the recruited study participants were positive for dengue IgG, indicating past exposure to dengue. Analysis on the demographic and socioeconomic variables suggested that high seroprevalence of dengue was significantly associated with those above 13 years old and a low household income of less than MYR500 (USD150). It was also associated with the vast presence of residential areas and the presence of a lake. Remote sensing analysis showed that higher land surface temperatures and lower land elevations also contributed to higher dengue seroprevalence. -e present study suggested that both demographic and geographical factors contributed to the increasing risk of contracting dengue among the OA living at the forest fringe areas of Peninsular Malaysia. -e OA, hence, remained vulnerable to dengue

Dengue death with evidence of hemophagocytic syndrome and dengue virus infection in the bone marrow

INTRODUCTION: HPS is a potentially life-threatening histiocytic disorder that has been described in various viral infections including dengue. Its involvement in severe and fatal dengue is probably more common but is presently under recognized. CASE DESCRIPTION: A 38-year-old female was admitted after 5 days of fever. She was deeply jaundiced, leukopenic and thrombocytopenic. Marked elevation of transaminases, hyperbilirubinemia and hypoalbuminemia were observed. She had deranged INR values and prolonged aPTT accompanied with hypofibrinogenemia. She also had splenomegaly. She was positive for dengue IgM. Five days later she became polyuric and CT brain image showed gross generalized cerebral edema. Her conditions deteriorated by day 9, became confused with GCS of 9/15. Her BMAT showed minimal histiocytes. Her serum ferritin level peaked at 13,670.00 µg/mL and her sCD163 and sCD25 values were markedly elevated at 4750.00 ng/mL and 4191.00 pg/mL, respectively. She succumbed to the disease on day 10 and examination of her tissues showed the presence of dengue virus genome in the bone marrow. DISCUSSION AND EVALUATION: It is described here, a case of fatal dengue with clinical features of HPS. Though BMAT results did not show the presence of macrophage hemophagocytosis, other laboratory features were consistent with HPS especially marked elevation of ferritin, sCD163 and sCD25. Detection of dengue virus in the patient’s bone marrow, fifteen days after the onset of fever was also consistent with the suggestion that the HPS is associated with dengue virus infection. CONCLUSIONS: The findings highlight HPS as a possible complication leading to severe dengue and revealed persistent dengue virus infection of the bone marrow. Detection of HPS markers; ferritin, sCD163 and sCD25, therefore, should be considered for early recognition of HPS-associated dengue

A reverse transcription loop-mediated isothermal amplification for broad coverage detection of Asian and African Zika virus lineages.

BACKGROUND: Early detection of Zika virus (ZIKV) infection during the viremia and viruria facilitates proper patient management and mosquito control measurement to prevent disease spread. Therefore, a cost-effective nucleic acid detection method for the diagnosis of ZIKV infection, especially in resource-deficient settings, is highly required. METHODS: In the present study, a single-tube reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for the detection of both the Asian and African-lineage ZIKV. The detection limit, strain coverage and cross-reactivity of the ZIKV RT-LAMP assay was evaluated. The sensitivity and specificity of the RT-LAMP were also evaluated using a total of 24 simulated clinical samples. The ZIKV quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay was used as the reference assay. RESULTS: The detection limit of the RT-LAMP assay was 3.73 ZIKV RNA copies (probit analysis, P ≤ 0.05). The RT-LAMP assay detected the ZIKV genomes of both the Asian and African lineages without cross-reacting with other arthropod-borne viruses. The sensitivity and specificity of the RT-LAMP assay were 90% (95% CI = 59.6-98.2) and 100% (95% CI = 78.5-100.0), respectively. The RT-LAMP assay detected ZIKV genome in 9 of 24 (37.5%) of the simulated clinical samples compared to 10 of 24 (41.7%) by qRT-PCR assay with a high level of concordance (κ = 0.913, P < 0.001). CONCLUSION: The RT-LAMP assay is applicable for the broad coverage detection of both the Asian and African ZIKV strains in resource-deficient settings

Seroprevalence of Borrelia burgdorferi among the indigenous people (Orang Asli) of Peninsular Malaysia

Introduction: Lyme disease has been well-described in the North America and European countries. However, information is still very limited in the developing countries including Malaysia. The Orang Asli (OA), the indigenous people of Peninsular Malaysia reside mostly in the forest and forest fringe areas abundant with the vector for Lyme disease. Here, we described the seroprevalence of Borellia burgdorferi (B. burgdorferi) among the OA and demographic variables that could be associated with seroprevalence. Methodology: A total of 16 OA villages distributed across 8 states in Peninsular Malaysia participated in this study. Sera obtained from 904 OA volunteers were screened for anti-B. burgdorferi IgG antibodies. ELISA results obtained and demographic information collected were analysed to identify possible variables associated with seroprevalence. Results: A total of 73 (8.1%) OA tested positive for anti-B. burgdorferi IgG antibodies. Among all the variables examined, village of residence (p = 0.045) was the only significant predictor for seropositivity. High (> 10.0%) prevalence was associated with three OA villages. Those living in one particular village were 1.65 times more likely to be seropositive as compared to other OA villages. Age, gender, marital status, household size, level of education, monthly household income and occupation were not significant predictors for seropositivity. Conclusion: Results of the present study support earlier findings that B. burgdorferi infection among Malaysians is currently under-recognized. Further studies will be needed at these locations to confirm the presence of Lyme disease among these populations

Molecular identification of adenovirus causing respiratory tract infection in pediatric patients at the University of Malaya Medical Center

<p>Abstract</p> <p>Background</p> <p>There are at least 51 adenovirus serotypes (AdV) known to cause human infections. The prevalence of the different human AdV (HAdV) serotypes varies among different regions. Presently, there are no reports of the prevalent HAdV types found in Malaysia. The present study was undertaken to identify the HAdV types associated primarily with respiratory tract infections (RTI) of young children in Malaysia.</p> <p>Methods</p> <p>Archived HAdV isolates from pediatric patients with RTI seen at the University of Malaya Medical Center (UMMC), Kuala Lumpur, Malaysia from 1999 to 2005 were used. Virus isolates were inoculated into cell culture and DNA was extracted when cells showed significant cytopathic effects. AdV partial hexon gene was amplified and the sequences together with other known HAdV hexon gene sequences were used to build phylogenetic trees. Identification of HAdV types found among young children in Malaysia was inferred from the phylograms.</p> <p>Results</p> <p>At least 2,583 pediatric patients with RTI sought consultation and treatment at the UMMC from 1999 to 2005. Among these patients, 48 (< 2%) were positive for HAdV infections. Twenty-seven isolates were recovered and used for the present study. Nineteen of the 27 (~70%) isolates belonged to HAdV species C (HAdV-C) and six (~22%) were of HAdV species B (HAdV-B). Among the HAdV-C species, 14 (~74%) of them were identified as HAdV type 1 (HAdV-1) and HAdV type 2 (HAdV-2), and among the HAdV-B species, HAdV type 3 (HAdV-3) was the most common serotype identified. HAdV-C species also was isolated from throat and rectal swabs of children with hand, foot, and mouth disease (HFMD). Two isolates were identified as corresponding to HAdV-F species from a child with HFMD and a patient with intestinal obstruction.</p> <p>Conclusions</p> <p>HAdV-1 and HAdV-2 were the most common HAdV isolated from pediatric patients who sought treatment for RTI at the UMMC from 1999 to 2005. HAdV-B, mainly HAdV-3, was recovered from ~22% of the patients. These findings provide a benchmark for future studies on the prevalence and epidemiology of HAdV types in Malaysia and in the region.</p

Detecting dengue outbreaks in Malaysia using geospatial techniques

Dengue is a complex disease with an increasing number of infections worldwide. This study aimed to analyse spatiotemporal dengue outbreaks using geospatial techniques and examine the effects of the weather on dengue outbreaks in the Klang Valley area, Kuala Lumpur, Malaysia. Daily weather variables including rainfall, temperature (maximum and minimum) and wind speed were acquired together with the daily reported dengue cases data from 2001 to 2011 and converted into geospatial format to identify whether there was a specific pattern of the dengue outbreaks. The association between these variables and dengue outbreaks was assessed using Spearman’s correlation. The result showed that dengue outbreaks consistently occurred in the study area during a 11-year study period. And that the strongest outbreaks frequently occurred in two high-rise apartment buildings located in Kuala Lumpur City centre. The results also show significant negative correlations between maximum temperature and minimum temperature on dengue outbreaks around the study area as well as in the area of the high-rise apartment buildings in Kuala Lumpur City centre.</jats:p

Molecular identification of adenovirus causing respiratory tract infection in pediatric patients at the University of Malaya Medical Center

Background There are at least 51 adenovirus serotypes (AdV) known to cause human infections. The prevalence of the different human AdV (HAdV) serotypes varies among different regions. Presently, there are no reports of the prevalent HAdV types found in Malaysia. The present study was undertaken to identify the HAdV types associated primarily with respiratory tract infections (RTI) of young children in Malaysia. Methods Archived HAdV isolates from pediatric patients with RTI seen at the University of Malaya Medical Center (UMMC), Kuala Lumpur, Malaysia from 1999 to 2005 were used. Virus isolates were inoculated into cell culture and DNA was extracted when cells showed significant cytopathic effects. AdV partial hexon gene was amplified and the sequences together with other known HAdV hexon gene sequences were used to build phylogenetic trees. Identification of HAdV types found among young children in Malaysia was inferred from the phylograms. Results At least 2,583 pediatric patients with RTI sought consultation and treatment at the UMMC from 1999 to 2005. Among these patients, 48 (< 2%) were positive for HAdV infections. Twenty-seven isolates were recovered and used for the present study. Nineteen of the 27 (~70%) isolates belonged to HAdV species C (HAdV-C) and six (~22%) were of HAdV species B (HAdV-B). Among the HAdV-C species, 14 (~74%) of them were identified as HAdV type 1 (HAdV-1) and HAdV type 2 (HAdV-2), and among the HAdV-B species, HAdV type 3 (HAdV-3) was the most common serotype identified. HAdV-C species also was isolated from throat and rectal swabs of children with hand, foot, and mouth disease (HFMD). Two isolates were identified as corresponding to HAdV-F species from a child with HFMD and a patient with intestinal obstruction. Conclusions HAdV-1 and HAdV-2 were the most common HAdV isolated from pediatric patients who sought treatment for RTI at the UMMC from 1999 to 2005. HAdV-B, mainly HAdV-3, was recovered from ~22% of the patients. These findings provide a benchmark for future studies on the prevalence and epidemiology of HAdV types in Malaysia and in the region