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Find video protocols related to scientific articles indexed in Pubmed.
Influenza-associated hospitalizations, Singapore, 2004-2008 and 2010-2012.
Emerging Infect. Dis.
PUBLISHED: 10-03-2014
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Studies of influenza-associated hospitalizations in tropical settings are lacking. To increase understanding of the effect of influenza in Singapore, we estimated the age-specific influenza-associated hospitalizations for pneumonia and influenza during 2004-2008 and 2010-2012. The rate of hospitalization was 28.3/100,000 person-years during 2004-2008 and 29.6/100,000 person-years during 2010-2012. The age-specific influenza-associated hospitalization rates followed a J-shaped pattern: rates in persons >75 years of age and in children <6 months of age were >47 times and >26 times higher, respectively, than those for persons 25-44 years of age. Across all ages during these 2 study periods, ?12% of the hospitalizations for pneumonia and influenza were attributable to influenza. The rates and proportions of hospitalizations for influenza, particularly among the very young and the elderly, are considerable in Singapore and highlight the importance of vaccination in protecting populations at risk.
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Comparative genomic analysis of malaria mosquito vector-associated novel pathogen Elizabethkingia anophelis.
Genome Biol Evol
PUBLISHED: 05-08-2014
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Acquisition of Elizabethkingia infections in intensive care units (ICUs) has risen in the past decade. Treatment of Elizabethkingia infections is challenging due to the lack of effective therapeutic regimens, leading to a high mortality rate. Elizabethkingia infections have long been attributed to Elizabethkingia meningoseptica. Recently, we used whole-genome sequencing to reveal that E. anophelis is the pathogenic agent for an Elizabethkingia outbreak at two ICUs. We performed comparative genomic analysis of seven hospital-isolated E. anophelis strains with five available Elizabethkingia spp. genomes deposited in the National Center for Biotechnology Information Database. A pan-genomic approach was applied to identify the core- and pan-genome for the Elizabethkingia genus. We showed that unlike the hospital-isolated pathogen E. meningoseptica ATCC 12535 strain, the hospital-isolated E. anophelis strains have genome content and organization similar to the E. anophelis Ag1 and R26 strains isolated from the midgut microbiota of the malaria mosquito vector Anopheles gambiae. Both the core- and accessory genomes of Elizabethkingia spp. possess genes conferring antibiotic resistance and virulence. Our study highlights that E. anophelis is an emerging bacterial pathogen for hospital environments.
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Performance assessment of the BD MAX Cdiff assay in comparison to Xpert C. difficile assay in a setting with very low prevalence of toxigenic Clostridium difficile PCR ribotype 027.
Anaerobe
PUBLISHED: 04-25-2014
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In a clinical setting with low prevalence of 'epidemic' PCR ribotype 027, the BD MAX Cdiff assay was found to be a suitable alternative to the Xpert C. difficile assay for the detection of toxigenic Clostridium difficile in samples which are reflex PCR tested after obtaining a discrepant immunoassay result. There was no significant difference between the sensitivities and specificities of both commercial molecular assays.
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Effectiveness of seasonal influenza vaccinations against laboratory-confirmed influenza-associated infections among Singapore military personnel in 2010-2013.
Influenza Other Respir Viruses
PUBLISHED: 04-07-2014
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Limited information is available about seasonal influenza vaccine effectiveness (VE) in tropical communities.
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Rate of decline of antibody titers to pandemic influenza A (H1N1-2009) by hemagglutination inhibition and virus microneutralization assays in a cohort of seroconverting adults in Singapore.
BMC Infect. Dis.
PUBLISHED: 04-06-2014
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The rate of decline of antibody titers to influenza following infection can affect results of serological surveys, and may explain re-infection and recurrent epidemics by the same strain.
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Prediction of major antibiotic resistance in Escherichia coli and Klebsiella pneumoniae in Singapore, USA and China using a limited set of gene targets.
Int. J. Antimicrob. Agents
PUBLISHED: 02-14-2014
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Antibiotic resistance in Gram-negative bacteria, especially Enterobacteriaceae, can be conferred by a large number of different acquired resistance genes, although it appears that relatively few dominate. A previous survey of Escherichia coli and Klebsiella pneumoniae isolates from Sydney, Australia, revealed that a limited set of genes could reliably predict resistance to third-generation cephalosporins (3GCs) and aminoglycosides. Here we tested E. coli and K. pneumoniae isolates with a cefotaxime, ceftriaxone and/or ceftazidime minimum inhibitory concentration of ? 2 ?g/mL from China and Singapore, with significantly higher resistance rates than Australia, as well as the USA. Few targets were needed to predict non-susceptibility to 3GCs (95/95; 100%) and gentamicin (47/51; 92%). The gene types detected here are consistent with previous surveys in similar countries with similar resistance rates, where the majority of 3GC resistance can be explained by blaCTX-M genes. This study identified a limited set of genes capable of predicting resistance to 3GC and aminoglycoside antibiotics and implies a restriction in the global resistance gene pool that can be exploited for diagnostic purposes.
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Patient-based transcriptome-wide analysis identify interferon and ubiquination pathways as potential predictors of influenza a disease severity.
PLoS ONE
PUBLISHED: 01-01-2014
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The influenza A virus is an RNA virus that is responsible for seasonal epidemics worldwide with up to five million cases of severe illness and 500,000 deaths annually according to the World Health Organization estimates. The factors associated with severe diseases are not well defined, but more severe disease is more often seen among persons aged >65 years, infants, pregnant women, and individuals of any age with underlying health conditions.
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Microsporidial keratoconjunctivitis after rugby tournament, Singapore.
Emerging Infect. Dis.
PUBLISHED: 08-23-2013
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We investigated an outbreak of 47 probable and 6 confirmed cases of microsporidial keratoconjunctivitis involving participants of an international rugby tournament in Singapore in April 2012.The mode of transmission was eye contact with soil. Vittaforma corneae was identified in 4 of 6 corneal scrapings and in 1 of 12 soil water samples.
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Clinical utility of RD1, RD9 and hsp65 based PCR assay for the identification of BCG in vaccinated children.
BMC Res Notes
PUBLISHED: 07-09-2013
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Mycobacterium bovis Bacille Calmette-Guerin (BCG) vaccine is widely administered to prevent tuberculosis. Vaccine complications are rare. However, when BCG-related adverse reactions arise there is a need to rapidly and reliably identify BCG from other members of the Mycobacterium tuberculosis complex (TBC). PCR assays based on the detection of the regions of difference (RD), in particular RD1 and RD9, have been invaluable in the identification of BCG. Prior to this study, specimens were identified through HPLC analysis at a local reference laboratory taking up to 2 weeks for a result. We sought to expedite the identification process by validating a RD1, RD9 and hsp65 PCR assay for the identification and differentiation of BCG from TBC.
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Comparative analysis of the genome sequences and replication profiles of chikungunya virus isolates within the East, Central and South African (ECSA) lineage.
Virol. J.
PUBLISHED: 05-28-2013
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A comparative analysis of the genomic and replication profiles of different geographical chikungunya virus (CHIKV) isolates of the East, Central and South African (ECSA) lineage was performed.
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Factors influencing infection by pandemic influenza A(H1N1)pdm09 over three epidemic waves in Singapore.
Influenza Other Respir Viruses
PUBLISHED: 05-05-2013
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Previous influenza pandemics had second and on occasion third waves in many countries that were at times more severe than the initial pandemic waves.
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Enterobacter cloacae producing an uncommon class A carbapenemase, IMI-1, from Singapore.
J. Med. Microbiol.
PUBLISHED: 04-04-2013
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In this study, we describe the characterization of an infrequently encountered class A carbapenemase, IMI-1, from a clinical Enterobacter cloacae isolate. The isolate had high levels of resistance to carbapenems but retained susceptibility to expanded-spectrum cephalosporins. The blaIMI-1 gene was chromosomally encoded. Detection of the IMI-1 producer highlights the diversity of carbapenemases in a local clinical setting.
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Mosquito cellular factors and functions in mediating the infectious entry of chikungunya virus.
PLoS Negl Trop Dis
PUBLISHED: 02-07-2013
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Chikungunya virus (CHIKV) is an arthropod-borne virus responsible for recent epidemics in the Asia Pacific regions. A customized gene expression microarray of 18,760 transcripts known to target Aedes mosquito genome was used to identify host genes that are differentially regulated during the infectious entry process of CHIKV infection on C6/36 mosquito cells. Several genes such as epsin I (EPN1), epidermal growth factor receptor pathway substrate 15 (EPS15) and Huntingtin interacting protein I (HIP1) were identified to be differentially expressed during CHIKV infection and known to be involved in clathrin-mediated endocytosis (CME). Transmission electron microscopy analyses further revealed the presence of CHIKV particles within invaginations of the plasma membrane, resembling clathrin-coated pits. Characterization of vesicles involved in the endocytic trafficking processes of CHIKV revealed the translocation of the virus particles to the early endosomes and subsequently to the late endosomes and lysosomes. Treatment with receptor-mediated endocytosis inhibitor, monodansylcadaverine and clathrin-associated drug inhibitors, chlorpromazine and dynasore inhibited CHIKV entry, whereas no inhibition was observed with caveolin-related drug inhibitors. Inhibition of CHIKV entry upon treatment with low-endosomal pH inhibitors indicated that low pH is essential for viral entry processes. CHIKV entry by clathrin-mediated endocytosis was validated via overexpression of a dominant-negative mutant of Eps15, in which infectious entry was reduced, while siRNA-based knockdown of genes associated with CME, low endosomal pH and RAB trafficking proteins exhibited significant levels of CHIKV inhibition. This study revealed, for the first time, that the infectious entry of CHIKV into mosquito cells is mediated by the clathrin-dependent endocytic pathway.
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OXA-181-producing Klebsiella pneumoniae establishing in Singapore.
BMC Infect. Dis.
PUBLISHED: 01-28-2013
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Carbapenemase producing Enterobacteriaceae are becoming a major public health concern globally, however, relatively little is known about the molecular and clinical epidemiology of these organisms in many parts of the world.
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Molecular characterization of newly emerged blaKPC-2-producing Klebsiella pneumoniae in Singapore.
J. Clin. Microbiol.
PUBLISHED: 11-23-2011
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In Asia, bla(KPC) detection has been limited to East Asia and not yet seen in Southeast Asia. We report four bla(KPC-2)-containing Klebsiella pneumoniae isolates from two different hospitals in Singapore. All isolates belonged to strain type 11 (ST11) and were indistinguishable by pulsed-field gel electrophoresis (PFGE). bla(KPC-2) was located on nonconjugative plasmids and flanked by mobile genetic structures composed of a partial Tn4401 transposon and a Tn3-based transposon which previously have been described only in Chinese isolates.
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Detection of an unusual van genotype in a vancomycin-resistant Enterococcus faecium hospital isolate.
J. Clin. Microbiol.
PUBLISHED: 10-12-2011
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We highlight the detection of a rare vanM genotype in Enterococcus faecium. This isolate exhibited a VanB phenotype, with high levels of resistance to vancomycin (MIC, >256 mg/liter) and susceptibility to teicoplanin (MIC, 1 mg/liter). It was, however, vanB negative by PCR. Further screening for other van loci revealed the presence of a complete vanM operon.
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Influenza disease burden in adults by subtypes following the initial epidemic of pandemic H1N1 in Singapore.
Influenza Other Respir Viruses
PUBLISHED: 08-31-2011
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Peaks of influenza activity in July 2009 and January 2010 were >90% pandemic H1N1 (pH1N1), but by May 2010, H3N2 predominated in hospital attendances (46·5%, versus 38·9% pH1N1); H3N2 hospital attendances were older (72·9% aged ?60 years versus 13·5% for pH1N1), but the age-stratified proportions admitted for pneumonia ]were similar. As at the end of the third epidemic wave in Singapore, pH1N1 cases in hospital attendances were still markedly younger than cases of H3N2 or influenza B, with little evidence for any changes in severity.
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Comparison of two nucleic acid amplification assays, the Xpert MTB/RIF assay and the amplified Mycobacterium Tuberculosis Direct assay, for detection of Mycobacterium tuberculosis in respiratory and nonrespiratory specimens.
J. Clin. Microbiol.
PUBLISHED: 08-24-2011
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We compared the performance of the Xpert MTB/RIF assay, a new real-time tuberculosis (TB) PCR test, with that of the Amplified Mycobacterium Tuberculosis Direct (MTD) assay using 162 respiratory and nonrespiratory specimens. Based on culture as the gold standard, the overall sensitivity and specificity for all sample types for the Xpert MTB/RIF assay were 90.9 and 89%, respectively, while for the MTD assay, the overall sensitivity and specificity were 97.3 and 87.1%, respectively. A higher proportion of total equivocal results were obtained for the MTD assay, at 10.5% (17/162), while the Xpert MTB/RIF assay generated 5.5% (9/162) of invalid reads.
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Increasing antibiotic resistance in Streptococcus pneumoniae colonizing children attending day-care centres in Singapore.
Respirology
PUBLISHED: 08-19-2011
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Streptococcus pneumoniae is an important cause of morbidity and mortality in both the paediatric and adult population. This study aimed to define pneumococcal colonization rates, and antibiotic resistance patterns across two periods a decade apart, and also assess the serotypes of colonizing strains in children in the era of early pneumococcal conjugate vaccine uptake in Singapore.
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Risk factors for pandemic (H1N1) 2009 seroconversion among adults, Singapore, 2009.
Emerging Infect. Dis.
PUBLISHED: 08-02-2011
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A total of 828 community-dwelling adults were studied during the course of the pandemic (H1N1) 2009 outbreak in Singapore during June-September 2009. Baseline blood samples were obtained before the outbreak, and 2 additional samples were obtained during follow-up. Seroconversion was defined as a >4-fold increase in antibody titers to pandemic (H1N1) 2009, determined by using hemagglutination inhibition. Men were more likely than women to seroconvert (mean adjusted hazards ratio [HR] 2.23, mean 95% confidence interval [CI] 1.26-3.93); Malays were more likely than Chinese to seroconvert (HR 2.67, 95% CI 1.04-6.91). Travel outside Singapore during the study period was associated with seroconversion (HR 1.76, 95% CI 1.11-2.78) as was use of public transport (HR 1.81, 95% CI 1.05-3.09). High baseline antibody titers were associated with reduced seroconversion. This study suggests possible areas for intervention to reduce transmission during future influenza outbreaks.
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Chikungunya virus neutralization antigens and direct cell-to-cell transmission are revealed by human antibody-escape mutants.
PLoS Pathog.
PUBLISHED: 07-18-2011
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Chikungunya virus (CHIKV) is an alphavirus responsible for numerous epidemics throughout Africa and Asia, causing infectious arthritis and reportedly linked with fatal infections in newborns and elderly. Previous studies in animal models indicate that humoral immunity can protect against CHIKV infection, but despite the potential efficacy of B-cell-driven intervention strategies, there are no virus-specific vaccines or therapies currently available. In addition, CHIKV has been reported to elicit long-lasting virus-specific IgM in humans, and to establish long-term persistence in non-human primates, suggesting that the virus might evade immune defenses to establish chronic infections in man. However, the mechanisms of immune evasion potentially employed by CHIKV remain uncharacterized. We previously described two human monoclonal antibodies that potently neutralize CHIKV infection. In the current report, we have characterized CHIKV mutants that escape antibody-dependent neutralization to identify the CHIKV E2 domain B and fusion loop "groove" as the primary determinants of CHIKV interaction with these antibodies. Furthermore, for the first time, we have also demonstrated direct CHIKV cell-to-cell transmission, as a mechanism that involves the E2 domain A and that is associated with viral resistance to antibody-dependent neutralization. Identification of CHIKV sub-domains that are associated with human protective immunity, will pave the way for the development of CHIKV-specific sub-domain vaccination strategies. Moreover, the clear demonstration of CHIKV cell-to-cell transmission and its possible role in the establishment of CHIKV persistence, will also inform the development of future anti-viral interventions. These data shed new light on CHIKV-host interactions that will help to combat human CHIKV infection and inform future studies of CHIKV pathogenesis.
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Subcutaneous immunization with baculovirus surface-displayed hemagglutinin of pandemic H1N1 Influenza A virus induces protective immunity in mice.
Clin. Vaccine Immunol.
PUBLISHED: 07-13-2011
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The protective immunity of baculovirus displaying influenza virus hemagglutinin (BacHA) against influenza 2009 H1N1 virus infection in a murine model was investigated. The results showed that mice vaccinated with live BacHA or an inactive form of adjuvanted BacHA had enhanced specific antibody responses and induced protective immunity against 2009 H1N1 virus infection, suggesting the potential of baculovirus as a live or inactivated vaccine.
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Comparability of different methods for estimating influenza infection rates over a single epidemic wave.
Am. J. Epidemiol.
PUBLISHED: 06-30-2011
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Estimation of influenza infection rates is important for determination of the extent of epidemic spread and for calculation of severity indicators. The authors compared estimated infection rates from paired and cross-sectional serologic surveys, rates of influenza like illness (ILI) obtained from sentinel general practitioners (GPs), and ILI samples that tested positive for influenza using data from similar periods collected during the 2009 H1N1 epidemic in Singapore. The authors performed sensitivity analyses to assess the robustness of estimates to input parameter uncertainties, and they determined sample sizes required for differing levels of precision. Estimates from paired seroconversion were 17% (95% Bayesian credible interval (BCI): 14, 20), higher than those from cross-sectional serology (12%, 95% BCI: 9, 17). Adjusted ILI estimates were 15% (95% BCI: 10, 25), and estimates computed from ILI and laboratory data were 12% (95% BCI: 8, 18). Serologic estimates were least sensitive to the risk of input parameter misspecification. ILI-based estimates were more sensitive to parameter misspecification, though this was lessened by incorporation of laboratory data. Obtaining a 5-percentage-point spread for the 95% confidence interval in infection rates would require more than 1,000 participants per serologic study, a sentinel network of 90 GPs, or 50 GPs when combined with laboratory samples. The various types of estimates will provide comparable findings if accurate input parameters can be obtained.
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Chikungunya virus envelope-specific human monoclonal antibodies with broad neutralization potency.
J. Immunol.
PUBLISHED: 01-28-2011
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Chikungunya virus (CHIKV) is an alphavirus responsible for numerous epidemics in Africa and Asia. Infection by CHIKV is often characterized by long-lasting, incapacitating arthritis, and some fatal cases have been described among elderly and newborns. Currently, there is no available vaccine or specific treatment against CHIKV. Blood B cells from a donor with history of CHIKV infection were activated, immortalized, amplified, and cloned. Two human mAbs against CHIKV, 5F10 and 8B10, were identified, sequenced, and expressed in recombinant form for characterization. In a plaque reduction neutralization test, 5F10 and 8B10 show mean IC(50) of 72 and 46 ng/ml, respectively. Moreover, both mAbs lead to a strong decrease in extracellular spreading of infectious viral particles from infected to uninfected cells. Importantly, the mAbs neutralize different CHIKV isolates from Singapore, Africa, and Indonesia, as well as Onyong-nyong virus, but do not recognize other alphaviruses tested. Both mAbs are specific for the CHIKV envelope: 5F10 binds to the E2 glycoprotein ectodomain and 8B10 to E1 and/or E2. In conclusion, these two unique human mAbs strongly, broadly, and specifically neutralize CHIKV infection in vitro and might become possible therapeutic tools against CHIKV infection, especially in individuals at risk for severe disease. Importantly, these mAbs will also represent precious tools for future studies on host-pathogen interactions and the rational design of vaccines against CHIKV.
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Galactomannan-guided preemptive vs. empirical antifungals in the persistently febrile neutropenic patient: a prospective randomized study.
Int. J. Infect. Dis.
PUBLISHED: 01-17-2011
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Patients with neutropenic fever after 4-7 days of broad-spectrum antibiotics are given antifungals empirically. This strategy may lead to over-treatment.
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VereFlu™: an integrated multiplex RT-PCR and microarray assay for rapid detection and identification of human influenza A and B viruses using lab-on-chip technology.
Arch. Virol.
PUBLISHED: 01-11-2011
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Threatening sporadic outbreaks of avian influenza and the H1N1 pandemic of 2009 highlight the need for rapid and accurate detection and typing of influenza viruses. In this paper, we describe the validation of the VereFlu™ Lab-on-Chip Influenza Assay, which is based on the integration of two technologies: multiplex reverse transcription (RT)-PCR followed by microarray amplicon detection. This assay simultaneously detects five influenza virus subtypes, including the 2009 pandemic influenza A (H1N1), seasonal H1N1, H3N2, H5N1 and influenza B virus. The VereFlu™ assay was clinically validated in Singapore and compared against reference methods of real-time PCR, virus detection by immunofluorescence of cell cultures and sequencing. A sensitivity and specificity of 96.8% and 92.8%, respectively, was demonstrated for pandemic H1N1; 95.7% and 100%, respectively, for seasonal H1N1; 91.2% and 97.6%, respectively, for seasonal H3N2; 95.2% and 100%, respectively, for influenza B. Additional evaluations carried out at the World Health Organization (WHO) Collaborating Centre, Melbourne, Australia, confirmed that the test was able to reliably detect H5N1. This portable, fast time-to-answer (3 hours) device is particularly suited for diagnostic applications of detection, differentiation and identification of human influenza virus subtypes.
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Emergence of oseltamivir-resistant pandemic (H1N1) 2009 virus within 48 hours.
Emerging Infect. Dis.
PUBLISHED: 09-30-2010
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An oseltamivir-resistant influenza A pandemic (H1N1) 2009 virus evolved and emerged from zero to 52% of detectable virus within 48 hours of a patients exposure to oseltamivir. Phylogenetic analysis and data gathered by pyrosequencing and cloning directly on clinical samples suggest that the mutant emerged de novo.
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Risk factors for pandemic (H1N1) 2009 virus seroconversion among hospital staff, Singapore.
Emerging Infect. Dis.
PUBLISHED: 09-30-2010
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We describe incidence and risk factors for pandemic (H1N1) 2009 virus infection in healthcare personnel during the June-September 2009 epidemic in Singapore. Personnel contributed 3 serologic samples during June-October 2009, with seroconversion defined as a ?4-fold increase in hemagglutination inhibition titers to pandemic (H1N1) 2009. Of 531 participants, 35 showed evidence of seroconversion. Seroconversion rates were highest in nurses (28/290) and lowest in allied health staff (2/116). Significant risk factors on multivariate analysis were being a nurse (adjusted odds ratio [aOR] 4.5, 95% confidence interval [CI] 1.0-19.6) and working in pandemic (H1N1) 2009 isolation wards (aOR 4.5, 95% CI 1.3-15.6). Contact with pandemic (H1N1) 2009-infected colleagues (aOR 2.5, 95% CI 0.9-6.6) and larger household size (aOR 1.2, 95% CI 1.0-1.4) were of borderline significance. Our study suggests that seroconversion was associated with occupational and nonoccupational risk factors.
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Effectiveness of public health measures in mitigating pandemic influenza spread: a prospective sero-epidemiological cohort study.
J. Infect. Dis.
PUBLISHED: 09-25-2010
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Few studies have validated the effectiveness of public health interventions in reducing influenza spread in real?life settings. We aim to validate these measures used during the 2009 pandemic.
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Entomologic and molecular investigation into Plasmodium vivax transmission in Singapore, 2009.
Malar. J.
PUBLISHED: 07-01-2010
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Singapore has been certified malaria free since November 1982 by the World Health Organization and despite occasional local transmission, the country has maintained the standing. In 2009, three clusters of malaria cases were reported in Singapore.
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Serological response in RT-PCR confirmed H1N1-2009 influenza a by hemagglutination inhibition and virus neutralization assays: an observational study.
PLoS ONE
PUBLISHED: 06-20-2010
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We describe the serological response following H1N1-2009 influenza A infections confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR).
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Oseltamivir ring prophylaxis for containment of 2009 H1N1 influenza outbreaks.
N. Engl. J. Med.
PUBLISHED: 06-19-2010
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From June 22 through June 25, 2009, four outbreaks of infection with the pandemic influenza A (H1N1) virus occurred in Singapore military camps. We report the efficacy of ring chemoprophylaxis (geographically targeted containment by means of prophylaxis) with oseltamivir to control outbreaks of 2009 H1N1 influenza in semiclosed environments.
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A new common mutation in the hemagglutinin of the 2009 (H1N1) influenza A virus.
PLoS Curr
PUBLISHED: 06-03-2010
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As the 2009 (H1N1) influenza A virus continues evolving, most mutations appear geographically and temporally confined. However, the latest surveillance data suggests emergence of a new prominent mutation, E391K, in the hemagglutinin (HA) that is globally on the rise. Interestingly, when modelled in the context of the available HA crystal structure, this mutation could alter salt bridge patterns and stability in a region of the HA oligomerization interface that is important for membrane fusion and also a known antigenic site. We discuss occurrence of HA-E391K in global surveillance data and associated clinical phenotypes from Singapore ranging from mostly mild to few severe symptoms, including sporadic vaccine failure. More clinical and experimental data are needed to determine if this mutation could alter the biology and fitness of the virus or if its increased occurrence is due to founder effects.
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Active infection of human blood monocytes by Chikungunya virus triggers an innate immune response.
J. Immunol.
PUBLISHED: 04-19-2010
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Chikungunya virus (CHIKV) is an alphavirus that causes chronic and incapacitating arthralgia in humans. To date, interactions between the immune system and the different stages of the virus life cycle remain poorly defined. We demonstrated for the first time that CHIKV Ags could be detected in vivo in the monocytes of acutely infected patients. Using in vitro experimental systems, whole blood and purified monocytes, we confirmed that monocytes could be infected and virus growth could be sustained. CHIKV interactions with monocytes, and with other blood leukocytes, induced a robust and rapid innate immune response with the production of specific chemokines and cytokines. In particular, high levels of IFN-alpha were produced rapidly after CHIKV incubation with monocytes. The identification of monocytes during the early phase of CHIKV infection in vivo is significant as infected monocyte/macrophage cells have been detected in the synovial tissues of chronically CHIKV-infected patients, and these cells may behave as the vehicles for virus dissemination. This may explain the persistence of joint symptoms despite the short duration of viremia. Our results provide a better understanding on the basic mechanisms of infection and early antiviral immune responses and will help in the development of future effective control strategies.
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2009 influenza A(H1N1) seroconversion rates and risk factors among distinct adult cohorts in Singapore.
JAMA
PUBLISHED: 04-15-2010
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Singapore experienced a single epidemic wave of 2009 influenza A(H1N1) with epidemic activity starting in late June 2009 and peaking in early August before subsiding within a month.
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Real-time epidemic monitoring and forecasting of H1N1-2009 using influenza-like illness from general practice and family doctor clinics in Singapore.
PLoS ONE
PUBLISHED: 03-15-2010
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Reporting of influenza-like illness (ILI) from general practice/family doctor (GPFD) clinics is an accurate indicator of real-time epidemic activity and requires little effort to set up, making it suitable for developing countries currently experiencing the influenza A (H1N1-2009) pandemic or preparing for subsequent epidemic waves.
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Development of a novel multiplex PCR for the detection and differentiation of Salmonella enterica serovars Typhi and Paratyphi A.
Res. Microbiol.
PUBLISHED: 03-03-2010
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In this study, we developed a multiplex polymerase chain reaction (mPCR) assay for pan-Salmonella detection as well as for specific detection of serovars Typhi and Paratyphi A. The assay detects members of the Salmonella genus by amplifying the outer membrane protein C (ompC). The presence of either Salmonella serovar Typhi or Paratyphi A is indicated by amplification of the putative regulatory protein gene STY4220, which is common to both serovars. Further differentiation of the serovars was achieved by targeting the intergenic region (SSPAI) between SSPA1723a and SSPA1724 in serovar Paratyphi A, and stgA, a fimbrial subunit protein, in serovar Typhi. mPCR was evaluated using 124 clinical and reference Salmonella serovars. S. enterica serovars Typhi and Paratyphi A were detected at 100% specificity and sensitivity. Each PCR reaction detected approximately 1 pg of Salmonella genomic DNA. Sensitivity of the PCR when tested on 8-h-enriched spiked blood samples of serovars Typhi and Paratyphi A was estimated at 4.5 x 10(4)-5.5 x 10(4)CFU/ml, with similar detection levels observed for spiked fecal samples. This mPCR could prove to be a useful diagnostic tool for the detection and differentiation of serovars Typhi and Paratyphi A.
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HLA class I restriction as a possible driving force for Chikungunya evolution.
PLoS ONE
PUBLISHED: 02-01-2010
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After two decades of quiescence, epidemic resurgence of Chikungunya fever (CHIKF) was reported in Africa, several islands in the Indian Ocean, South-East Asia and the Pacific causing unprecedented morbidity with some cases of fatality. Early phylogenetic analyses based on partial sequences of Chikungunya virus (CHIKV) have led to speculation that the virus behind recent epidemics may result in greater pathogenicity. To understand the reasons for these new epidemics, we first performed extensive analyses of existing CHIKV sequences from its introduction in 1952 to 2009. Our results revealed the existence of a continuous genotypic lineage, suggesting selective pressure is active in CHIKV evolution. We further showed that CHIKV is undergoing mild positive selection, and that site-specific mutations may be driven by cell-mediated immune pressure, with occasional changes that resulted in the loss of human leukocyte antigen (HLA) class I-restricting elements. These findings provide a basis to understand Chikungunya virus evolution and reveal the power of post-genomic analyses to understand CHIKV and other viral epidemiology. Such an approach is useful for studying the impact of host immunity on pathogen evolution, and may help identify appropriate antigens suitable for subunit vaccine formulations.
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Inactivated trivalent seasonal influenza vaccine induces limited cross-reactive neutralizing antibody responses against 2009 pandemic and 1934 PR8 H1N1 strains.
Vaccine
PUBLISHED: 01-14-2010
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In June 2009, we conducted a prospective study in Singapore on 51 individuals to determine their serologic responses before and following receipt of the 2009 Southern Hemisphere seasonal influenza vaccine.
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Re-emergence of Chikungunya virus in South-east Asia: virological evidence from Sri Lanka and Singapore.
J. Gen. Virol.
PUBLISHED: 12-02-2009
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Chikungunya fever swept across many South and South-east Asian countries, following extensive outbreaks in the Indian Ocean Islands in 2005. However, molecular epidemiological data to explain the recent spread and evolution of Chikungunya virus (CHIKV) in the Asian region are still limited. This study describes the genetic Characteristics and evolutionary relationships of CHIKV strains that emerged in Sri Lanka and Singapore during 2006-2008. The viruses isolated in Singapore also included those imported from the Maldives (n=1), India (n=2) and Malaysia (n=31). All analysed strains belonged to the East, Central and South African (ECSA) lineage and were evolutionarily more related to Indian than to Indian Ocean Islands strains. Unique genetic characteristics revealed five genetically distinct subpopulations of CHIKV in Sri Lanka and Singapore, which were likely to have emerged through multiple, independent introductions. The evolutionary network based on E1 gene sequences indicated the acquisition of an alanine to valine 226 substitution (E1-A226V) by virus strains of the Indian sublineage as a key evolutionary event that contributed to the transmission and spatial distribution of CHIKV in the region. The E1-A226V substitution was found in 95.7 % (133/139) of analysed isolates in 2008, highlighting the widespread establishment of mutated CHIKV strains in Sri Lanka, Singapore and Malaysia. As the E1-A226V substitution is known to enhance the transmissibility of CHIKV by Aedes albopictus mosquitoes, this observation has important implications for the design of vector control strategies to fight the virus in regions at risk of chikungunya fever.
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Entomologic and virologic investigation of Chikungunya, Singapore.
Emerging Infect. Dis.
PUBLISHED: 09-16-2009
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Local transmission of chikungunya, a debilitating mosquito-borne viral disease, was first reported in Singapore in January 2008. After 3 months of absence, locally acquired Chikungunya cases resurfaced in May 2008, causing an outbreak that resulted in a total of 231 cases by September 2008. The circulating viruses were related to East, Central, and South African genotypes that emerged in the Indian Ocean region in 2005. The first local outbreak was due to a wild-type virus (alanine at codon 226 of the envelope 1 gene) and occurred in an area where Aedes aegypti mosquitoes were the primary vector. Strains isolated during subsequent outbreaks showed alanine to valine substitution (A226V) and largely spread in areas predominated by Ae. albopictus mosquitoes. These findings led to a revision of the current vector control strategy in Singapore. This report highlights the use of entomologic and virologic data to assist in the control of chikungunya in disease-endemic areas.
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Chikungunya: a bending reality.
Microbes Infect.
PUBLISHED: 09-10-2009
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Chikungunya fever is an acute illness caused by the arbovirus Chikungunya virus. The virus is transmitted primarily in a sylvatic cycle involving the Aedes mosquitoes. Since 2005, a Chikungunya fever outbreak of unprecedented magnitude occurred on several Indian Ocean islands. Since then, the disease has spread to many parts of the world due to imported cases among travellers returning from epidemic areas. Chikungunya virus causes a wide spectrum of illness including fever, a characteristic rash, disabling joint symptoms which can sometimes become severe that lasts months. This review summarises on this history of Chikungunya fever, host specificity, the characteristics of Chikungunya virus, clinical features of disease and current control measures. It focuses on how the re-emergence of an old changed the outlook of managing arboviral diseases in the present social and public health context.
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Influenza excess mortality from 1950-2000 in tropical Singapore.
PLoS ONE
PUBLISHED: 09-01-2009
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Tropical regions have been shown to exhibit different influenza seasonal patterns compared to their temperate counterparts. However, there is little information about the burden of annual tropical influenza epidemics across time, and the relationship between tropical influenza epidemics compared with other regions.
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Molecular epidemiology of vancomycin-resistant enterococci in Singapore.
Pathology
PUBLISHED: 08-12-2009
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To characterise the mechanism of glycopeptide resistance, genetic relatedness, and pathogenicity factors in isolates of vancomycin-resistant enterococci (VRE) in Singapore.
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The incidence of human bocavirus infection among children admitted to hospital in Singapore.
J. Med. Virol.
PUBLISHED: 06-09-2009
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Human bocavirus (HBoV) is a parvovirus, belonging to the genus Bocavirus. The virus was identified recently in Sweden, and has now been detected in several different countries. Although it is associated with lower respiratory tract infections in pediatric patients, the incidence of HBoV infection in a developed country in South East Asia, has not been examined. The objective of this study was to determine the importance of HBoV as a cause of lower respiratory tract infections among children admitted to hospital in Singapore. Five hundred nasopharyngeal swabs were collected from anonymized pediatric patients admitted to the Kandang Kerbau Womens and Childrens Hospital for acute respiratory infections. The specimens were tested for the presence of HBoV using polymerase chain reactions. HBoV was detected in 8.0% of the patients tested, and a majority of these HBoV patients exhibited lower respiratory tract infections. A significant level of coinfection with respiratory syncytial viruses and rhinoviruses was also observed in these HBoV patients. The data suggest that HBoV is an important cause of lower respiratory tract infections among children admitted to hospital in Singapore, and is the first study examining the incidence of HBoV infection in a developed country in South East Asia.
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Pseudo-outbreak of Rhizobium radiobacter infection resulting from laboratory contamination of saline solution.
J. Clin. Microbiol.
PUBLISHED: 05-20-2009
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We report a pseudo-outbreak of Rhizobium radiobacter infections resulting from contamination by a saline dispenser in the microbiology laboratory. Isolates from clinical specimens had identical antimicrobial susceptibilities and electrophoretic fingerprints. The episode resolved with autoclaving of the dispenser. This demonstrates the importance of timely, thorough investigation of unusual organisms, particularly when they appear as a cluster.
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Dual life-threatening pathologies presenting simultaneously.
BMJ Case Rep
PUBLISHED: 05-10-2009
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A 70-year-old male presented to hospital with both anterior ST elevation myocardial infarction and spontaneous oesophageal rupture (Boerhaaves syndrome). He underwent primary angioplasty and stenting for a lesion of the left anterior descending in addition to cardiothoracic surgery for the oesophageal rupture. This combination of pathologies is a rare entity and often difficult to diagnose. To date, only a few cases have been reported.
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Detection and genetic characterisation of qnrB in hospital isolates of Klebsiella pneumoniae in Singapore.
Int. J. Antimicrob. Agents
PUBLISHED: 03-11-2009
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Polymerase chain reaction (PCR) screening of 116 ciprofloxacin-resistant Klebsiella pneumoniae hospital isolates for the presence of qnr genes that mediate plasmid quinolone resistance revealed that none were positive for qnrA or qnrS. However, qnrB was detected in ca. 5.2% of the isolates. Southern hybridisation demonstrated that the qnrB-hybridising plasmids were large (>70kb) and capable of transferring quinolone resistance by conjugation. Sequence analysis of the qnrB genes detected in this study showed that they were identical to previously identified qnrB1, qnrB4 and qnrB6 genes, although a novel variant designated qnrB20 was also identified. Analysis of the genetic environment around the cloned qnrB genes showed that they were present in diverse plasmid backbones, sometimes within novel genetic contexts, but always associated with mobile or transposable elements.
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Possible nosocomial transmission of measles in unvaccinated children in a Singapore public hospital.
Western Pac Surveill Response J
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Measles is an acute, highly communicable viral disease, with measles outbreaks usually occurring in settings where there are unvaccinated populations. After being notified of a cluster of five measles cases in a Singapore public hospital in August 2011, the Ministry of Health Singapore conducted an outbreak investigation.
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Teacher led school-based surveillance can allow accurate tracking of emerging infectious diseases - evidence from serial cross-sectional surveys of febrile respiratory illness during the H1N1 2009 influenza pandemic in Singapore.
BMC Infect. Dis.
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Schools are important foci of influenza transmission and potential targets for surveillance and interventions. We compared several school-based influenza monitoring systems with clinic-based influenza-like illness (ILI) surveillance, and assessed the variation in illness rates between and within schools.
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Longitudinal analysis of the human antibody response to Chikungunya virus infection: implications for serodiagnosis and vaccine development.
J. Virol.
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Chikungunya virus (CHIKV) is an alphavirus which causes chronic and incapacitating arthralgia in humans. Although previous studies have shown that antibodies against the virus are produced during and after infection, the fine specificity of the antibody response against CHIKV is not known. Here, using plasma from patients at different times postinfection, we characterized the antibody response against various proteins of the virus. We have shown that the E2 and E3 glycoproteins and the capsid and nsP3 proteins are targets of the anti-CHIKV antibody response. Moreover, we have identified the different regions in these proteins which contain the linear epitopes recognized by the anti-CHIKV antibodies and determined their structural localization. Data also illustrated the effect of a single K(252)Q amino acid change at the E2 glycoprotein that was able to influence antibody binding and interaction between the antibodies and epitope because of the changes of epitope-antibody binding capacity. This study provides important knowledge that will not only aid in the understanding of the immune response to CHIKV infection but also provide new knowledge in the design of modern vaccine development. Furthermore, these pathogen-specific epitopes could be used for future seroepidemiological studies that will unravel the molecular mechanisms of human immunity and protection from CHIKV disease.
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Early neutralizing IgG response to Chikungunya virus in infected patients targets a dominant linear epitope on the E2 glycoprotein.
EMBO Mol Med
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Chikungunya virus (CHIKV) and related arboviruses have been responsible for large epidemic outbreaks with serious economic and social impact. The immune mechanisms, which control viral multiplication and dissemination, are not yet known. Here, we studied the antibody response against the CHIKV surface antigens in infected patients. With plasma samples obtained during the early convalescent phase, we showed that the naturally-acquired IgG response is dominated by IgG3 antibodies specific mostly for a single linear epitope E2EP3. E2EP3 is located at the N-terminus of the E2 glycoprotein and prominently exposed on the viral envelope. E2EP3-specific antibodies are neutralizing and their removal from the plasma reduced the CHIKV-specific antibody titer by up to 80%. Screening of E2EP3 across different patient cohorts and in non-human primates demonstrated the value of this epitope as a good serology detection marker for CHIKV infection already at an early stage. Mice vaccinated by E2EP3 peptides were protected against CHIKV with reduced viremia and joint inflammation, providing a pre-clinical basis for the design of effective vaccine against arthralgia-inducing CHIKV and other alphaviruses.
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JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.