BackgroundDengue infection has been an important and serious public health concern in Malaysia ever since its first reported case here in 1902. Nevertheless, to our knowledge, no nationwide investigation has been carried out to determine the actual magnitude of dengue endemicity in the Malaysian population. In this study, we describe a cross sectional seroepidemiology study of dengue IgG seroprevalence in the Malaysian adult population.FindingsFrom 1000 subjects (35-74 years old), 91.6% subjects were found to be dengue seropositive. Age is found to be a significant risk factor associated with dengue seroposivity, where the seroprevalence increased with every 10 year increase in age. Nevertheless, gender and ethnicity did not have an effect. Interestingly, there were similar seroprevalence rates between urban and rural samples, showing that dengue is presently not confined to urban areas in Malaysia.ConclusionsHigh dengue IgG seropositivity found in the population is an indication that dengue might be endemic in Malaysia for a long time into the future. Public awareness, proper vector control and vigilant surveillance are critical to keep the infection rates low and to prevent outbreaks.

BackgroundIn 1998, Malaysia experienced its first chikungunya virus (CHIKV) outbreak in the suburban areas followed by another two in 2006 (rural areas) and 2008 (urban areas), respectively. Nevertheless, there is still a lack of documented data regarding the magnitude of CHIKV exposure in the Malaysian population. The aim of this study was to determine the extent of chikungunya virus infection in healthy Malaysian adults residing in outbreak-free locations.MethodsA cross sectional study of chikungunya (CHIK) seroprevalence was carried out in 2009 amongst The Malaysian Cohort participants living in four states (Kuala Lumpur, Selangor, Pahang and Negeri Sembilan). A total of 945 participants were randomly identified for the study. Potential risk factors for CHIK infection were determined via questionnaires, and IgG antibodies against CHIK were detected by an enzyme-linked immunosorbent assay. Logistic regression identified risk factors associated with CHIK seropositivity, while geographical information system was used for visual and spatial analysis.ResultsFrom the 945 serum samples tested, 5.9% was positive for CHIK IgG. Being male, Malay, rural occupancy and Negeri Sembilan residency were identified as univariate predictors for CHIK seropositivity, while multivariate analysis identified being male and rural occupancy as risk factors.ConclusionsThis study provided evidence that CHIK is slowly emerging in Malaysia. Although the current baseline seroprevalence is low in this country, increasing number of CHIK cases reported to the Malaysia Ministry of Health imply the possibility of CHIK virus becoming endemic in Malaysia.

Background A periodic serosurvey of dengue seroprevalence is vital to determine the prevalence of dengue in countries where this disease is endemic. This study aimed to determine the prevalence of dengue immunoglobulin G (IgG) seropositivity among healthy Malaysian adults living in urban and rural areas. Methods A total of 2598 serum samples (1417 urban samples, 1181 rural samples) were randomly collected from adults ages 35–74 y. The presence of the dengue IgG antibody and neutralising antibodies to dengue virus (DENV) 1–4 was determined using enzyme-linked immunosorbent assay and the plaque reduction neutralisation test assay, respectively. Results The prevalence of dengue IgG seropositivity was 85.39% in urban areas and 83.48% in rural areas. The seropositivity increased with every 10-y increase in age. Ethnicity was associated with dengue seropositivity in urban areas but not in rural areas. The factors associated with dengue seropositivity were sex and working outdoors. In dengue IgG-positive serum samples, 98.39% of the samples had neutralising antibodies against DENV3, but only 70.97% of them had neutralising antibodies against DENV4. Conclusion The high seroprevalence of dengue found in urban and rural areas suggests that both urban and rural communities are vital for establishing and sustaining DENV transmission in Malaysia.

Malaysia is a country with an intermediate endemicity for hepatitis B. As the country moves toward hepatitis B and C elimination, population-based estimates are necessary to understand the burden of hepatitis B and C for evidence-based policy-making. Hence, this study aims to estimate the prevalence of hepatitis B and C in Malaysia. A total of 1458 participants were randomly selected from The Malaysian Cohort (TMC) aged 35 to 70 years between 2006 and 2012. All blood samples were tested for hepatitis B and C markers including hepatitis B surface antigen (HBsAg), anti-hepatitis B core antibody (anti-HBc), antibodies against hepatitis C virus (anti-HCV). Those reactive for hepatitis C were further tested for HCV RNA genotyping. The sociodemographic characteristics and comorbidities were used to evaluate their associated risk factors. Descriptive analysis and multivariable analysis were done using Stata 14. From the samples tested, 4% were positive for HBsAg (95% CI 2.7–4.7), 20% were positive for anti-HBc (95% CI 17.6–21.9) and 0.3% were positive for anti-HCV (95% CI 0.1–0.7). Two of the five participants who were reactive for anti-HCV had the HCV genotype 1a and 3a. The seroprevalence of HBV and HCV infection in Malaysia is low and intermediate, respectively. This population-based study could facilitate the planning and evaluation of the hepatitis B and C control program in Malaysia.

Neutralization assay is a technique that detects and quantifies neutralizing antibody in serum samples by calculating the percentage of reduction of virus activity, as the concentration of virus used is usually constant. Neutralizing antibody titer is conventionally determined by calculating the percentage reduction in total virus infectivity by counting and comparing number of plaques (localized area of infection due to cytopathic effect) with a standard amount of virus. Conventional neutralizing test uses plaque-reduction neutralization test (PRNT) to determine neutralizing antibody titers against Chikungunya virus (CHIKV). Here we describe the plaque reduction neutralization assay (PRNT) using Vero cell lines to obtain neutralizing antibody titers.