Displaying publications 221 - 240 of 246 in total

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  1. Fulltext Group IV Getah Virus in Culex Mosquitoes, Malaysia
    Sam SS, Mohamed-Romai-Noor NA, Teoh BT, Hamim ZR, Ng HY, Abd-Jamil J, et al.
    Emerg Infect Dis, 2022 Feb;28(2):475-477.
    PMID: 35076371 DOI: 10.3201/eid2802.204887
    A new Getah virus (GETV) strain, B254, was isolated from Culex fuscocephalus mosquitoes captured at Mount Ophir, Malaysia, in 2012. Phylogenetic analyses revealed that GETV B254 is distinct from the old Malaysia GETV MM2021 strain but closely related to group IV GETV from Russia (LEIV16275Mag), China (YN12031), and Thailand (GETV/SW/Thailand/2017).
  2. Serological evidence of DENV, JEV, and ZIKV among the indigenous people (Orang Asli) of Peninsular Malaysia
    Khor CS, Mohd-Rahim NF, Hassan H, Tan KK, Zainal N, Teoh BT, et al.
    J Med Virol, 2020 08;92(8):956-962.
    PMID: 31814135 DOI: 10.1002/jmv.25649
    Dengue virus (DENV), Japanese encephalitis virus (JEV), and Zika virus (ZIKV) are mosquito-borne flavivirus of medical importance in tropical countries such as Malaysia. However, much remains unknown regarding their prevalence among the underserved indigenous people (Orang Asli) living in communities in the forest fringe areas of Peninsular Malaysia. Information on the prevalence of diseases is necessary to elevate the effectiveness of disease control and preventive measures. This study aimed to determine the seroprevalence of the three major flaviviruses among the Orang Asli and investigate the association between demographic factors and seropositivities. Sampling activities were conducted in the Orang Asli villages to obtain serum samples and demographic data from consenting volunteers. The presence of DENV, JEV, and ZIKV immunoglobulin G (IgG) antibodies in the sera were examined using commercial enzyme-linked immunosorbent assay kits. A focus reduction neutralization assay was performed to measure virus-specific neutralizing antibodies. A total of 872 serum samples were obtained from the Orang Asli volunteers. Serological assay results revealed that DENV IgG, JEV IgG, and ZIKV IgG seropositivities among the Orang Asli were at 4.9%, 48.4%, and 13.2%, respectively. Neutralizing antibodies (FRNT50 ≥ 1:40) against JEV and ZIKV were found in 86.7% and 100.0%, respectively, out of the samples tested. Positive serology to all three viruses corresponded significantly to the age of the volunteers with increasing seropositivity in older volunteers. Findings from the study suggest that Orang Asli are at significant risk of contracting JEV and ZIKV infections despite the lack of active transmission of the viruses in the country.
  3. Detection and confirmation of dengue pre- and postintroduction of dengue NS1-antigen test at the University Malaya Medical Centre: An observational study
    Abd-Jamil J, Azizan NS, Che-Mat-Seri NA, Yaacob CN, Samsudin NI, Mahfodz NH, et al.
    J Med Virol, 2021 08;93(8):4714-4719.
    PMID: 33421159 DOI: 10.1002/jmv.26790
    Early diagnosis of dengue is important to ensure proper management of patients and effective implementation of control measures. The present study was undertaken to determine the outcome of the implementation of dengue NS1-antigen (Ag) rapid diagnostic test (RDT) in the confirmation of dengue at the first patient hospital visit at the University Malaya Medical Centre. A total of 1036 and 1097 sera from the year 2008 and 2015 were used, representing samples from before and after dengue NS1-Ag RDT was implemented as routine diagnostic at the hospital. Results showed that similar dengue confirmation percentage (56%) was made in 2008 and 2015, regardless of the main laboratory diagnostic method used. Confirmation of dengue, however, increased to 68% and 73% when dengue NS1-Ag test or dengue immunoglobulin M-capture enzyme-linked immunosorbent assay was used as the second test for the 2008 and 2015 samples, respectively. Detection of dengue virus (DENV) using multiplex reverse transcription-polymerase chain reaction (RT-PCR) showed that DENV-1 was the highest in circulation in 2008 and that both DENV-1 and DENV-2 were dominant in 2015. In summary, the present study demonstrated that the introduction and use of the dengue NS1-Ag RDT did not change or compromise confirmation of dengue, highlighting the advantage of using the method. With the reducing cost of molecular detection tools, DENV detection using RT-PCR remains a viable option for further confirmation of dengue in hospital settings.
  4. Fulltext A comparison of assays for accurate copy number measurement of the low-affinity Fc gamma receptor genes FCGR3A and FCGR3B
    Haridan US, Mokhtar U, Machado LR, Abdul Aziz AT, Shueb RH, Zaid M, et al.
    PLoS One, 2015;10(1):e0116791.
    PMID: 25594501 DOI: 10.1371/journal.pone.0116791
    The FCGR3 locus encoding the low affinity activating receptor FcγRIII, plays a vital role in immunity triggered by cellular effector and regulatory functions. Copy number of the genes FCGR3A and FCGR3B has previously been reported to affect susceptibility to several autoimmune diseases and chronic inflammatory conditions. However, such genetic association studies often yield inconsistent results; hence require assays that are robust with low error rate. We investigated the accuracy and efficiency in estimating FCGR3 CNV by comparing Sequenom MassARRAY and paralogue ratio test-restriction enzyme digest variant ratio (PRT-REDVR). In addition, since many genetic association studies of FCGR3B CNV were carried out using real-time quantitative PCR, we have also included the evaluation of that method's performance in estimating the multi-allelic CNV of FCGR3B. The qPCR assay exhibited a considerably broader distribution of signal intensity, potentially introducing error in estimation of copy number and higher false positive rates. Both Sequenom and PRT-REDVR showed lesser systematic bias, but Sequenom skewed towards copy number normal (CN = 2). The discrepancy between Sequenom and PRT-REDVR might be attributed either to batch effects noise in individual measurements. Our study suggests that PRT-REDVR is more robust and accurate in genotyping the CNV of FCGR3, but highlights the needs of multiple independent assays for extensive validation when performing a genetic association study with multi-allelic CNVs.
  5. Fulltext An evaluation of the World Health Organization's 1997 and 2009 dengue classifications in hospitalized dengue patients in Malaysia
    Zakaria Z, Zainordin NA, Sim BL, Zaid M, Haridan US, Aziz AT, et al.
    J Infect Dev Ctries, 2014 Jul;8(7):869-75.
    PMID: 25022297 DOI: 10.3855/jidc.4283
    INTRODUCTION: The latest revised version of the World Health Organization's dengue classification was released in 2009. A handful of studies have taken initiatives to evaluate the old and revised guidelines to determine early signs and symptoms of severe dengue. This retrospective study aimed to compare the classification of dengue using both the 1997 and 2009 guidelines in a selected cohort of dengue patients from Peninsular Malaysia between 2008 and 2012.
    METHODOLOGY: Adult dengue patients were recruited from tertiary hospitals in two different states, Selangor and Kelantan, in Peninsular Malaysia. Their clinical manifestations were assessed.
    RESULTS: A total of 281 confirmed dengue patients were enrolled; the mean duration of illness at admission was five days. Of these, 88.6%, 10.7%, and 0.7% were classified according to the 1997 guidelines as having dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS), respectively. When the WHO 2009 guidelines were applied, 17.1%, 78.3%, and 4.6% were classified as dengue without warning signs, dengue with warning signs, and severe dengue, respectively.
    CONCLUSIONS: Our data suggests that the revised WHO 2009 guidelines stratify a much larger proportion of patients into a category that requires a higher level of medical and nursing care.
  6. Indirect effects of cigarette butt waste on the dengue vector Aedes aegypti (Diptera: Culicidae)
    Dieng H, Rajasaygar S, Ahmad AH, Rawi CS, Ahmad H, Satho T, et al.
    Acta Trop, 2014 Feb;130:123-30.
    PMID: 24239749 DOI: 10.1016/j.actatropica.2013.11.001
    Despite major insecticide-based vector control programs, dengue continues to be a major threat to public health in urban areas. The reasons for this failure include the emergence of insecticide resistance and the narrowing of the spectrum of efficient products. Cigarette butts (CBs), the most commonly discarded piece of waste, also represent a major health hazard to human and animal life. CBs are impregnated with thousands of chemical compounds, many of which are highly toxic and none of which has history of resistance in mosquitoes. This study was performed to examine whether exposure to CB alters various biological parameters of parents and their progeny. We examined whether the mosquito changes its ovipositional behaviors, egg hatching, reproductive capacity, longevity and fecundity in response to CB exposure at three different concentrations. Females tended to prefer microcosms containing CBs for egg deposition than those with water only. There were equivalent rates of eclosion success among larvae from eggs that matured in CB and water environments. We also observed decreased life span among adults that survived CB exposure. Extracts of CB waste have detrimental effects on the fecundity and longevity of its offspring, while being attractive to its gravid females. These results altogether indicate that CB waste indirectly affect key adult life traits of Aedes aegypti and could conceivably be developed as a novel dengue vector control strategy, referring to previously documented direct toxicity on the larval stage. But this will require further research on CB waste effects on non-target organisms including humans.
  7. Fulltext Colonized Aedes albopictus and its sexual performance in the wild: implications for SIT technology and containment
    Hamady D, Ruslan NB, Ahmad AH, Rawi CS, Ahmad H, Satho T, et al.
    Parasit Vectors, 2013;6:206.
    PMID: 23856274 DOI: 10.1186/1756-3305-6-206
    Mating is a physiological process of crucial importance underlying the size and maintenance of mosquito populations. In sterile and incompatible insect technologies (SIT and IIT), mating is essential for mass production, persistence, and success of released individuals, and is a central parameter for judging the effectiveness of SIT/IIT programs. Some mosquitoes have an enormous reproductive potential for both themselves and pathogens and mating may contribute to persistence of infection in nature. As Aedes albopictus can transmit flaviviruses both sexually and horizontally, and as infected insects are usually derived from laboratory colonies, we investigated the implications of mating between a long-term laboratory colony of Ae. albopictus and wild populations.
  8. Turning cigarette butt waste into an alternative control tool against an insecticide-resistant mosquito vector
    Dieng H, Rajasaygar S, Ahmad AH, Ahmad H, Rawi CS, Zuharah WF, et al.
    Acta Trop, 2013 Dec;128(3):584-90.
    PMID: 23999373 DOI: 10.1016/j.actatropica.2013.08.013
    Annually, 4.5 trillion cigarette butts (CBs) are flicked into our environment. Evidence exists that CB waste is deadly to aquatic life, but their lethality to the aquatic life of the main dengue vector is unknown. CBs are full of toxicants that occur naturally, during planting and manufacturing, which may act as larvicidal agents. We assessed Aedes aegypti vulnerability to Marlboro butts during its development. Overall, CBs showed insecticidal activities against larvae. At early phases of development, mortality rates were much higher in two CBs solution (2CBSol) and 3CBSol microcosms (MICRs). Larval survival gradually decreased with development in 1CBSol-MICRs. However, in great presence of CBs, mortality was high even for the late developmental stages. These results suggest that A. aegypti larvae are vulnerable to CB presence in their habitats, but this effect was seen most during the early developmental phases and in the presence of increased amounts of cigarette remnants. CB filters are being used as raw material in many sectors, i.e., brick, art, fashion, plastic industries, as a practical solution to the pollution problem, the observed butt waste toxicity to mosquito larvae open new avenues for the identification of novel insecticide products.
  9. Fulltext Evolution of Influenza B Virus in Kuala Lumpur, Malaysia, between 1995 and 2008
    Sam IC, Su YC, Chan YF, Nor'E SS, Hassan A, Jafar FL, et al.
    J Virol, 2015 Sep;89(18):9689-92.
    PMID: 26136576 DOI: 10.1128/JVI.00708-15
    Influenza B virus causes significant disease but remains understudied in tropical regions. We sequenced 72 influenza B viruses collected in Kuala Lumpur, Malaysia, from 1995 to 2008. The predominant circulating lineage (Victoria or Yamagata) changed every 1 to 3 years, and these shifts were associated with increased incidence of influenza B. We also found poor lineage matches with recommended influenza virus vaccine strains. While most influenza B virus lineages in Malaysia were short-lived, one circulated for 3 to 4 years.
  10. Fulltext The Risk of Transfusion-Transmitted Hepatitis E Virus: Evidence from Seroprevalence Screening of Blood Donations
    Wong LP, Lee HY, Khor CS, Abdul-Jamil J, Alias H, Abu-Amin N, et al.
    Indian J Hematol Blood Transfus, 2021 Apr 16.
    PMID: 33879981 DOI: 10.1007/s12288-021-01428-7
    Throughout the world, there has been growing concern over the risk of hepatitis E virus (HEV) transmission via blood transfusion. The present study screened blood donor samples for anti-HEV immunoglobulin M (IgM) and immunoglobulin G (IgG). The prevalence of HEV infection was assessed on a total of 1,003 archived serum samples obtained from the National Blood Centre, Malaysia. The samples were collected from healthy blood donor from Klang Valley between 2017 and 2018. All samples were tested for IgM and IgG antibodies to HEV using enzyme-linked immunosorbent assays (ELISA). HEV-specific IgG antibodies were detected in 31/1003 (3.1%; 95% confidence interval [CI] 2.1%-4.4%) and IgM in 9/1003 (0.9%; 95% CI 0.4%-1.7%) samples. In bivariate analysis, there was no significant difference in the prevalence of anti-HEV IgG with respect to gender and district of origin. Although not statistically significant, males had higher odds of having anti-HEV IgG than females (odds ratio [OR] = 2.86; 95% CI 0.95-8.64). All anti-HEV IgG positive individuals were people of Chinese descent. Anti-HEV IgG increased significantly with age, from 0.6% (95% CI 0.1%-2.6%) of 18-30-year-old donors to 7.4% (95% CI 2.7%-17.0%) of donors older than 50 years and was highest among non-professional workers (5.3%; 95% CI 2.5%-10.5%). Increasing age and a non-professional occupation remained significant predictors for anti-HEV IgG in the multivariable analysis. Screening of blood donations for HEV in Malaysia is important to safeguard the health of transfusion recipients. The higher rates of HEV infection in blood from older donors and donors who are non-professional workers may provide insights into targeted groups for blood screening.
  11. Seroprevalence of Q Fever Among the Indigenous People (Orang Asli) of Peninsular Malaysia
    Khor CS, Mohd-Rahim NF, Hassan H, Chandren JR, Nore SS, Johari J, et al.
    Vector Borne Zoonotic Dis, 2018 03;18(3):131-137.
    PMID: 29336685 DOI: 10.1089/vbz.2017.2153
    Q fever is a disease caused by Coxiella burnetii. It is a disease of public health concern in many parts of the world. In this study, we described the seroprevalence of Q fever among selected populations of Orang Asli (OA), indigenous people, many of whom live within the forest fringe areas of Peninsular Malaysia. Serum samples were obtained from 887 OA participants from selected villages. Samples were analyzed for the presence of IgG antibodies reactive against C. burnetii by enzyme-linked immunosorbent assay. Statistical methods were used to identify possible associations between seropositivity for C. burnetii and a number of demographic variables obtained from the questionnaires. In total, 9.6% (n = 85/887) of the serum samples were reactive to C. burnetii. Statistical results suggest that elderly male OA residing in OA village, Bukit Payung, were most likely to be tested seropositive for C. burnetii. This study suggests that OA are at a significant risk of contracting C. burnetii infection, and both demographic and geographic factors are important contributors to this risk. Further prospective studies are needed to establish the true burden of C. burnetii infection within the indigenous population as well as within Peninsular Malaysia as a whole.
  12. CPAF, HSP60 and MOMP antigens elicit pro-inflammatory cytokines production in the peripheral blood mononuclear cells from genital Chlamydia trachomatis-infected patients
    Cheong HC, Lee CYQ, Cheok YY, Shankar EM, Sabet NS, Tan GMY, et al.
    Immunobiology, 2019 01;224(1):34-41.
    PMID: 30477893 DOI: 10.1016/j.imbio.2018.10.010
    BACKGROUND: Persistent inflammation caused by Chlamydia trachomatis in the female genital compartment represents one of the major causes of pelvic inflammatory disease (PID), ectopic pregnancy and infertility in females. Here, we examined the pro-inflammatory cytokine response following stimulation with three different types of C. trachomatis antigens, viz. chlamydial protease-like factor (CPAF), heat shock protein 60 (HSP60) and major outer membrane protein (MOMP).

    METHODS: A total of 19 patients with genital C. trachomatis infection and 10 age-matched healthy controls were recruited for the study. Peripheral blood mononuclear cells (PBMCs) isolated from genital C. trachomatis-infected females were cultured in the presence of CPAF, HSP60 and MOMP antigens, and cytokines were measured by ELISA assay.

    RESULTS: We reported that pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) were robustly secreted following antigenic exposure. Notably, CPAP and MOMP were more potent in triggering IL-1β, as compared to HSP60. Elevated levels of the proinflammatory cytokines were also noted in the samples infected with plasmid-bearing C. trachomatis as compared to those infected with plasmid-free strains.

    CONCLUSIONS: Our study highlights distinct ability of chlamydial antigens in triggering pro-inflammatory response in the host immune cells.

  13. Fulltext Diversity of endocervical microbiota associated with genital Chlamydia trachomatis infection and infertility among women visiting obstetrics and gynecology clinics in Malaysia
    Cheong HC, Yap PSX, Chong CW, Cheok YY, Lee CYQ, Tan GMY, et al.
    PLoS One, 2019;14(11):e0224658.
    PMID: 31738795 DOI: 10.1371/journal.pone.0224658
    The cervical microbiota constitutes an important protective barrier against the invasion of pathogenic microorganisms. A disruption of microbiota within the cervical milieu has been suggested to be a driving factor of sexually transmitted infections. These include Chlamydia trachomatis which frequently causes serious reproductive sequelae such as infertility in women. In this study, we profiled the cervical microbial composition of a population of 70 reproductive-age Malaysian women; among which 40 (57.1%) were diagnosed with genital C. trachomatis infection, and 30 (42.8%) without C. trachomatis infection. Our findings showed a distinct compositional difference between the cervical microbiota of C. trachomatis-infected subjects and subjects without C. trachomatis infection. Specifically, significant elevations of mostly strict and facultative anaerobes such as Streptococcus, Megasphaera, Prevotella, and Veillonella in the cervical microbiota of C. trachomatis-positive women were detected. The results from the current study highlights an interaction of C. trachomatis with the environmental microbiome in the endocervical region.
  14. Fulltext Seroprevalence of Borrelia burgdorferi among the indigenous people (Orang Asli) of Peninsular Malaysia
    Khor CS, Hassan H, Mohd-Rahim NF, Chandren JR, Nore SS, Johari J, et al.
    J Infect Dev Ctries, 2019 05 31;13(5):449-454.
    PMID: 32053515 DOI: 10.3855/jidc.11001
    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.

  15. Fulltext Emergence of B.1.524(G) SARS-CoV-2 in Malaysia during the third COVID-19 epidemic wave
    Tan KK, Tan JY, Wong JE, Teoh BT, Tiong V, Abd-Jamil J, et al.
    Sci Rep, 2021 11 11;11(1):22105.
    PMID: 34764315 DOI: 10.1038/s41598-021-01223-4
    The COVID-19 pandemic first emerged in Malaysia in Jan 2020. As of 12th Sept 2021, 1,979,698 COVID-19 cases that occurred over three major epidemic waves were confirmed. The virus contributing to the three epidemic waves has not been well-studied. We sequenced the genome of 22 SARS-CoV-2 strains detected in Malaysia during the second and the ongoing third wave of the COVID-19 epidemic. Detailed phylogenetic and genetic variation analyses of the SARS-CoV-2 isolate genomes were performed using these newly determined sequences and all other available sequences. Results from the analyses suggested multiple independent introductions of SARS-CoV-2 into Malaysia. A new B.1.524(G) lineage with S-D614G mutation was detected in Sabah, East Malaysia and Selangor, Peninsular Malaysia on 7th October 2020 and 14th October 2020, respectively. This new B.1.524(G) group was not the direct descendant of any of the previously detected lineages. The new B.1.524(G) carried a set of genetic variations, including A701V (position variant frequency = 0.0007) in Spike protein and a novel G114T mutation at the 5'UTR. The biological importance of the specific mutations remained unknown. The sequential appearance of the mutations, however, suggests that the spread of the new B.1.524(G) lineages likely begun in Sabah and then spread to Selangor. The findings presented here support the importance of SARS-CoV-2 full genome sequencing as a tool to establish an epidemiological link between cases or clusters of COVID-19 worldwide.
  16. Fulltext Lactococcus lactis Strain Plasma Intake Suppresses the Incidence of Dengue Fever-like Symptoms in Healthy Malaysians: A Randomized, Double-Blind, Placebo-Controlled Trial
    Khor CS, Tsuji R, Lee HY, Nor'e SS, Sahimin N, Azman AS, et al.
    Nutrients, 2021 Dec 16;13(12).
    PMID: 34960061 DOI: 10.3390/nu13124507
    Dengue fever (DF) is a mosquito-borne disease still with no effective treatment or vaccine available. A randomized, placebo-controlled, double-blinded, parallel-group trial was undertaken to evaluate the efficacy of oral intake of Lactococcus lactis strain plasma (LC-Plasma) on the presentation and severity of DF-like symptoms among healthy volunteers. Study participants (320) were assigned into two groups, and consumed either placebo or LC-Plasma tablets (approximately 100 billion cells/day) for 8 weeks. The clinical symptoms of DF were self-recorded through questionnaires, and exposure to DENV was determined by serum antibody and/or DENV antigen tests. No significant differences between groups were observed for exposure to DENV, or the symptomatic ratio. Results obtained showed that participants from the LC-Plasma group reported a significant reduction in the cumulative incidence days of DF-like symptoms, which include fever (p < 0.001), muscle pain (p < 0.005), joint pain (p < 0.001), and pain behind the eyes (p < 0.001), compared to that of the placebo group. Subgroup analysis revealed a significantly (p < 0.05) reduced severity score in the LC-Plasma group when study sites were separately analyzed. Overall, our findings suggest that LC-Plasma supplementation reduces the cumulative days with DF-like symptoms, and the severity of the symptoms. Daily oral intake of LC-Plasma, hence, is shown to mitigate the DF-like symptoms.
  17. Fulltext Epidemiological serosurvey of chikungunya fever post outbreak at Tanjung Sepat, Malaysia
    Khor CS, Teoh BT, Sam SS, Khoo HY, Azizan NS, CheMatSeri A, et al.
    J Infect Dev Ctries, 2023 Jan 31;17(1):118-124.
    PMID: 36795935 DOI: 10.3855/jidc.16613
    INTRODUCTION: Chikungunya fever is a mosquito-borne viral disease that usually presents with prominent arthralgia. An outbreak of chikungunya fever was reported in Tanjung Sepat, Malaysia in 2019. The outbreak was limited in size with a low number of cases being reported. The present study sought to determine the possible variables that could have affected the transmission of the infection.

    METHODOLOGY: A cross-sectional study involving 149 healthy adult volunteers from Tanjung Sepat was performed soon after the outbreak had subsided. All the participants donated blood samples and completed the questionnaires. Laboratory detection of anti-CHIKV IgM and IgG antibodies was performed using enzyme-linked immunoassays (ELISA). Risk factors associated with chikungunya seropositivity were determined using logistic regression.

    RESULTS: The majority (72.5%, n = 108) of the study participants tested positive for CHIKV antibodies. Only 8.3% (n = 9) of the participants out of all the seropositive volunteers had an asymptomatic infection. Participants who resided with a febrile (p < 0.05, Exp(B) = 2.2, confidence interval [CI] 1.3-3.6) or a CHIKV-diagnosed person (p < 0.05, Exp(B) = 2.1, CI 1.2-3.6) in the same household were found likely to be tested positive for CHIKV antibodies.

    CONCLUSIONS: Findings from the study support that asymptomatic CHIKV infections and indoor transmission occurred during the outbreak. Hence, widespread community testing and indoor use of mosquito repellent are among the possible measures that can be implemented to reduce CHIKV transmission during an outbreak.

  18. Fulltext MERS-CoV seroconversion amongst Malaysian Hajj pilgrims returning from the Middle East, 2016-2018: results from the MERCURIAL multiyear prospective cohort study
    Johari J, Hontz RD, Pike BL, Husain T, Rusli N, Mohd-Zain R, et al.
    Emerg Microbes Infect, 2023 Dec;12(1):2208678.
    PMID: 37101375 DOI: 10.1080/22221751.2023.2208678
    Prospective cohort study to investigate the potential exposure to the Middle East Respiratory Syndrome-Coronavirus (MERS-CoV) following Hajj pilgrims is still very limited. Here, we report the antibody seroconversion study results obtained from successive three years cohort studies (2016-2018) involving the Malaysian Hajj pilgrims returning from the Middle East. A cohort study of Hajj pilgrims from Malaysia enrolled 2,863 participants from 2016-2018, all of whom consented to provide paired blood samples for both pre- and post-Hajj travel to the Middle East. ELISAs and micro-neutralization assays were performed to detect the presence of MERS-CoV IgG antibodies. Sociodemographic data, symptoms experienced during Hajj, and history of exposure to camels or camel products were recorded using structured pre- and post-Hajj questionnaires. A 4-fold increase in anti-MERS-CoV IgG between paired pre-Hajj and post-Hajj serum samples in twelve participants was observed. None of the twelve ELISA-positive sera had detectable levels of virus-neutralizing antibodies. All reportedly had mild symptoms of respiratory symptoms at a certain point during the pilgrimage, implying mild or asymptomatic infections. No association between post-Hajj serum positivity and a history of exposure to camels or camel products was obtained. Findings from the study suggest that serologic conversion to MERS-CoV occurred in at least 0.6% of the Hajj pilgrims returning from the Middle East. Since all the seroconvertants had mild to no symptoms during the sampling period, it highlights the likelihood of occurrence of only low infectivity spillover infections among the Hajj pilgrims.
  19. Fulltext Nucleoside Analogs with Selective Antiviral Activity against Dengue Fever and Japanese Encephalitis Viruses
    Zandi K, Bassit L, Amblard F, Cox BD, Hassandarvish P, Moghaddam E, et al.
    Antimicrob Agents Chemother, 2019 Jul;63(7).
    PMID: 31061163 DOI: 10.1128/AAC.00397-19
    Dengue virus (DENV) and Japanese encephalitis virus (JEV) are important arthropod-borne viruses from the Flaviviridae family. DENV is a global public health problem with significant social and economic impacts, especially in tropical and subtropical areas. JEV is a neurotropic arbovirus endemic to east and southeast Asia. There are no U.S. FDA-approved antiviral drugs available to treat or to prevent DENV and JEV infections, leaving nearly one-third of the world's population at risk for infection. Therefore, it is crucial to discover potent antiviral agents against these viruses. Nucleoside analogs, as a class, are widely used for the treatment of viral infections. In this study, we discovered nucleoside analogs that possess potent and selective anti-JEV and anti-DENV activities across all serotypes in cell-based assay systems. Both viruses were susceptible to sugar-substituted 2'-C-methyl analogs with either cytosine or 7-deaza-7-fluoro-adenine nucleobases. Mouse studies confirmed the anti-DENV activity of these nucleoside analogs. Molecular models were assembled for DENV serotype 2 (DENV-2) and JEV RNA-dependent RNA polymerase replication complexes bound to nucleotide inhibitors. These models show similarities between JEV and DENV-2, which recognize the same nucleotide inhibitors. Collectively, our findings provide promising compounds and a structural rationale for the development of direct-acting antiviral agents with dual activity against JEV and DENV infections.
  20. Fulltext Current vector research challenges in the greater Mekong subregion for dengue, Malaria, and Other Vector-Borne Diseases: A report from a multisectoral workshop March 2019
    Christofferson RC, Parker DM, Overgaard HJ, Hii J, Devine G, Wilcox BA, et al.
    PLoS Negl Trop Dis, 2020 Jul;14(7):e0008302.
    PMID: 32730249 DOI: 10.1371/journal.pntd.0008302
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