ABSTRACT Communicable diseases continue to pose a threat to the health of Singaporeans. Despite a... more ABSTRACT Communicable diseases continue to pose a threat to the health of Singaporeans. Despite advances in medical science and the implementation of good public health infrastructure and hygiene measures, new and old diseases continue to emerge and re-emerge. Family physicians are often the first point of contact for patients infected with communicable diseases. Understanding the epidemiology of communicable diseases in the community would enable the family physician to better manage, prevent and control these ...
Introduction: Clostridium difficile infection (CDI) is an increasingly recognized nosocomial infe... more Introduction: Clostridium difficile infection (CDI) is an increasingly recognized nosocomial infection in Singapore. Surveillance methods include laboratory reporting of Clostridium difficile toxin assays (CDTA) or use of International Classification of Diseases, 9 th Revision (ICD-9) discharge code 008.45. Previous US studies showed good correlation between CDTA and ICD-9 codes. However, the use of ICD-9 codes for CDI surveillance has not been validated in other healthcare settings.
strict containment measures for pandemic (H1N1) 2009 with enhanced surveillance and hospital isol... more strict containment measures for pandemic (H1N1) 2009 with enhanced surveillance and hospital isolation. In the fi rst month, seasonal infl uenza, predominantly virus subtype H3N2, was diagnosed for 32% of patients with acute febrile respiratory illness. Our fi ndings underscore the high prevalence of seasonal infl uenza in Singapore.
We compared strategies for stockpiling neuraminidase inhibitors to treat and prevent influenza in... more We compared strategies for stockpiling neuraminidase inhibitors to treat and prevent influenza in Singapore. Costbenefit and cost-effectiveness analyses, with Monte Carlo simulations, were used to determine economic outcomes. A pandemic in a population of 4.2 million would result in an estimated 525-1,775 deaths, 10,700-38,600 hospitalization days, and economic costs of $0.7 to $2.2 billion Singapore dollars. The treatment-only strategy had optimal economic benefits: stockpiles of antiviral agents for 40% of the population would save an estimated 418 lives and $414 million, at a cost of $52.6 million per shelf-life cycle of the stockpile. Prophylaxis was economically beneficial in highrisk subpopulations, which account for 78% of deaths, and in pandemics in which the death rate was >0.6%. Prophylaxis for pandemics with a 5% case-fatality rate would save 50,000 lives and $81 billion. These models can help policymakers weigh the options for pandemic planning.
Background: The sensitivity and specificity of two in-house MAC-ELISA assays were tested and comp... more Background: The sensitivity and specificity of two in-house MAC-ELISA assays were tested and compared with the performance of commercially-available CTK lateral flow rapid test and EUROIMMUN IFA assays for the detection of anti-Chikungunya virus (CHIKV) IgM. Each MAC-ELISA assay used a whole virus-based antigen derived from genetically distinct CHIKV strains involved in two chikungunya disease outbreaks in Singapore (2008); a January outbreak strain with alanine at amino acid residue 226 of the E1 glycoprotein (CHIKV-A226) and a May-to-September outbreak strain that possessed valine at the same residue (CHIKV-226V). We report differences in IgM detection efficacy of different assays between the two outbreaks. The sensitivities of two PCR protocols were also tested.
Abstract We used a regression model to examine the impact of influenza on death rates in tropical... more Abstract We used a regression model to examine the impact of influenza on death rates in tropical Singapore for the period 1996–2003. Influenza A (H3N2) was the predominant circulating influenza virus subtype, with consistently significant and robust effect on mortality rates.
Abstract Chikungunya virus (CHIKV) is a mosquito-borne arthralgia arbovirus that is reemergent in... more Abstract Chikungunya virus (CHIKV) is a mosquito-borne arthralgia arbovirus that is reemergent in sub-Saharan Africa and Southeast Asia. CHIKV infection has been shown to be self-limiting, but the molecular mechanisms of the innate immune response that control CHIKV replication remain undefined.
Background Dengue and chikungunya are co-circulating vector-borne diseases with substantial overl... more Background Dengue and chikungunya are co-circulating vector-borne diseases with substantial overlap in clinical presentations. It is important to differentiate between them during first presentation as their management, especially for dengue hemorrhagic fever (DHF), is different. This study compares their clinical presentation in Singapore adults to derive predictors to assist doctors in diagnostic decision-making.
ABSTRACT Hepatitis B is a disease of public health importance in Singapore. A study was conducted... more ABSTRACT Hepatitis B is a disease of public health importance in Singapore. A study was conducted in 1999 to estimate the overall and gender-, age-and ethnicspecific prevalence of hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg) and antibody to hepatitis B surface antigen in the Singapore population. A cross-sectional sample of the Singapore population constituting 4,698 Singapore residents aged 18-69 years was surveyed.
Methods Four hemifacial microsomic patients treated with unilateral mandibular distraction were r... more Methods Four hemifacial microsomic patients treated with unilateral mandibular distraction were recalled. Changes in maxillary width and height, occlusal height, ramus height, mandibular length, and chin position were quantified by using the posteroanterior and 45 lateral oblique cephalographs. Predistraction and postdistraction measurements were taken over a 5-year period. The data were analyzed by using paired t tests and ANOVA.
Background The World Health Organization (WHO) and the Centers for Disease Control and Prevention... more Background The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) recommend the use of alcohol handrubs to prevent health care-associated infections. However, the efficacy and time effectiveness of different alcohol handrubbing protocols have yet to be evaluated.
Abstract An oseltamivir-resistant influenza A pandemic (H1N1) 2009 virus evolved and emerged from... more Abstract An oseltamivir-resistant influenza A pandemic (H1N1) 2009 virus evolved and emerged from zero to 52% of detectable virus within 48 hours of a patient's exposure to oseltamivir. Phylogenetic analysis and data gathered by pyrosequencing and cloning directly on clinical samples suggest that the mutant emerged de novo.
RESULTS: During early disease onset, naturally-acquired anti-CHIKV antibodies from patients mostl... more RESULTS: During early disease onset, naturally-acquired anti-CHIKV antibodies from patients mostly target a linear dominant epitope 'E2EP3'located at the N-terminus of the E2 glycoprotein. Up to 80% of anti-CHIKV antibodies are specific against E2EP3 and removal of anti-E2EP3 antibodies partially reversed the neutralizing effects. Sero-positivity of E2EP3 validated across different patient cohorts confirmed that E2EP3 could be a good serology marker for early CHIKV detection.
ABSTRACT Understanding factors associated with de novo daptomycin-nonsusceptible Enterococcus (DN... more ABSTRACT Understanding factors associated with de novo daptomycin-nonsusceptible Enterococcus (DNSE) infections will aid in better understanding the mechanisms of daptomycin nonsusceptibility. We conducted a case-control study to compare patients with DNSE infections who were daptomycin treatment naïve (n= 9) and those with DNSE infections who had exposure to daptomycin (n= 13).
Background Pandemic influenza (H1N1) 2009 is susceptible to oseltamivir. There are few reports on... more Background Pandemic influenza (H1N1) 2009 is susceptible to oseltamivir. There are few reports on its clinical and virologic response to oseltamivir. Methods During the pandemic containment response in Singapore, all patients with positive polymerase chain reaction (PCR) results for pandemic influenza (H1N1) 2009 were hospitalized, given oseltamivir for 5 days, and discharged when daily PCR results for combined nasal and throat swab samples became negative.
Methods We compared CDI rates based on CDTA to ICD-9 codes for all discharges in 2007 from our ho... more Methods We compared CDI rates based on CDTA to ICD-9 codes for all discharges in 2007 from our hospital to determine sensitivity and specificity of ICD-9 codes. Demographic and hospitalization data were analyzed to determine predictors for missing ICD-9 codes. Results During 2007, there were 56,352 discharges. Of these, 268 tested CDTA-positive but only 133 were assigned the CDI ICD-9 code. A total of 141 discharges had the ICD-9 code; 8 were CDTA-negative, the rest were CDTA-positive.
ABSTRACT Understanding factors associated with de novo Daptomycin non-susceptible Enterococcus (D... more ABSTRACT Understanding factors associated with de novo Daptomycin non-susceptible Enterococcus (DNSE) infections will aid in better understanding of the mechanisms of daptomycin non-susceptibility. We conducted a case-control study to compare patients with DNSE infections that were daptomycin treatment naïve (n= 9) and those who had exposure to daptomycin (n= 13).
ABSTRACT Chikungunya is a re-emerging mosquito-borne viral infection that has spread from East Af... more ABSTRACT Chikungunya is a re-emerging mosquito-borne viral infection that has spread from East Africa to Indian Ocean islands and re-emerged in India since 2004. In Malaysia, chikungunya re-emerged after a hiatus of seven years, causing a localised outbreak in a north-western coastal town in 2006 and subsequently widespread outbreaks in 2008. Since the first local outbreak of chikungunya in Singapore in January 2008, chikungunya infections have been increasingly reported in Singapore.
Abstract Introduction: Highly active antiretroviral therapy (HAART) has greatly changed the epide... more Abstract Introduction: Highly active antiretroviral therapy (HAART) has greatly changed the epidemiology of human immunodeficiency virus (HIV) mortality. The aim of this study is to compare the causes of death and factors associated with early death in HIV-infected persons in the pre-and peri-highly active antiretroviral therapy (HAART) periods. Materials and Methods: We conducted a retrospective review of 483 HIV-infected persons who were diagnosed with HIV from 1985 to 2000, and had died within 5 years of the diagnosis.
ABSTRACT Communicable diseases continue to pose a threat to the health of Singaporeans. Despite a... more ABSTRACT Communicable diseases continue to pose a threat to the health of Singaporeans. Despite advances in medical science and the implementation of good public health infrastructure and hygiene measures, new and old diseases continue to emerge and re-emerge. Family physicians are often the first point of contact for patients infected with communicable diseases. Understanding the epidemiology of communicable diseases in the community would enable the family physician to better manage, prevent and control these ...
Introduction: Clostridium difficile infection (CDI) is an increasingly recognized nosocomial infe... more Introduction: Clostridium difficile infection (CDI) is an increasingly recognized nosocomial infection in Singapore. Surveillance methods include laboratory reporting of Clostridium difficile toxin assays (CDTA) or use of International Classification of Diseases, 9 th Revision (ICD-9) discharge code 008.45. Previous US studies showed good correlation between CDTA and ICD-9 codes. However, the use of ICD-9 codes for CDI surveillance has not been validated in other healthcare settings.
strict containment measures for pandemic (H1N1) 2009 with enhanced surveillance and hospital isol... more strict containment measures for pandemic (H1N1) 2009 with enhanced surveillance and hospital isolation. In the fi rst month, seasonal infl uenza, predominantly virus subtype H3N2, was diagnosed for 32% of patients with acute febrile respiratory illness. Our fi ndings underscore the high prevalence of seasonal infl uenza in Singapore.
We compared strategies for stockpiling neuraminidase inhibitors to treat and prevent influenza in... more We compared strategies for stockpiling neuraminidase inhibitors to treat and prevent influenza in Singapore. Costbenefit and cost-effectiveness analyses, with Monte Carlo simulations, were used to determine economic outcomes. A pandemic in a population of 4.2 million would result in an estimated 525-1,775 deaths, 10,700-38,600 hospitalization days, and economic costs of $0.7 to $2.2 billion Singapore dollars. The treatment-only strategy had optimal economic benefits: stockpiles of antiviral agents for 40% of the population would save an estimated 418 lives and $414 million, at a cost of $52.6 million per shelf-life cycle of the stockpile. Prophylaxis was economically beneficial in highrisk subpopulations, which account for 78% of deaths, and in pandemics in which the death rate was >0.6%. Prophylaxis for pandemics with a 5% case-fatality rate would save 50,000 lives and $81 billion. These models can help policymakers weigh the options for pandemic planning.
Background: The sensitivity and specificity of two in-house MAC-ELISA assays were tested and comp... more Background: The sensitivity and specificity of two in-house MAC-ELISA assays were tested and compared with the performance of commercially-available CTK lateral flow rapid test and EUROIMMUN IFA assays for the detection of anti-Chikungunya virus (CHIKV) IgM. Each MAC-ELISA assay used a whole virus-based antigen derived from genetically distinct CHIKV strains involved in two chikungunya disease outbreaks in Singapore (2008); a January outbreak strain with alanine at amino acid residue 226 of the E1 glycoprotein (CHIKV-A226) and a May-to-September outbreak strain that possessed valine at the same residue (CHIKV-226V). We report differences in IgM detection efficacy of different assays between the two outbreaks. The sensitivities of two PCR protocols were also tested.
Abstract We used a regression model to examine the impact of influenza on death rates in tropical... more Abstract We used a regression model to examine the impact of influenza on death rates in tropical Singapore for the period 1996–2003. Influenza A (H3N2) was the predominant circulating influenza virus subtype, with consistently significant and robust effect on mortality rates.
Abstract Chikungunya virus (CHIKV) is a mosquito-borne arthralgia arbovirus that is reemergent in... more Abstract Chikungunya virus (CHIKV) is a mosquito-borne arthralgia arbovirus that is reemergent in sub-Saharan Africa and Southeast Asia. CHIKV infection has been shown to be self-limiting, but the molecular mechanisms of the innate immune response that control CHIKV replication remain undefined.
Background Dengue and chikungunya are co-circulating vector-borne diseases with substantial overl... more Background Dengue and chikungunya are co-circulating vector-borne diseases with substantial overlap in clinical presentations. It is important to differentiate between them during first presentation as their management, especially for dengue hemorrhagic fever (DHF), is different. This study compares their clinical presentation in Singapore adults to derive predictors to assist doctors in diagnostic decision-making.
ABSTRACT Hepatitis B is a disease of public health importance in Singapore. A study was conducted... more ABSTRACT Hepatitis B is a disease of public health importance in Singapore. A study was conducted in 1999 to estimate the overall and gender-, age-and ethnicspecific prevalence of hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg) and antibody to hepatitis B surface antigen in the Singapore population. A cross-sectional sample of the Singapore population constituting 4,698 Singapore residents aged 18-69 years was surveyed.
Methods Four hemifacial microsomic patients treated with unilateral mandibular distraction were r... more Methods Four hemifacial microsomic patients treated with unilateral mandibular distraction were recalled. Changes in maxillary width and height, occlusal height, ramus height, mandibular length, and chin position were quantified by using the posteroanterior and 45 lateral oblique cephalographs. Predistraction and postdistraction measurements were taken over a 5-year period. The data were analyzed by using paired t tests and ANOVA.
Background The World Health Organization (WHO) and the Centers for Disease Control and Prevention... more Background The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) recommend the use of alcohol handrubs to prevent health care-associated infections. However, the efficacy and time effectiveness of different alcohol handrubbing protocols have yet to be evaluated.
Abstract An oseltamivir-resistant influenza A pandemic (H1N1) 2009 virus evolved and emerged from... more Abstract An oseltamivir-resistant influenza A pandemic (H1N1) 2009 virus evolved and emerged from zero to 52% of detectable virus within 48 hours of a patient's exposure to oseltamivir. Phylogenetic analysis and data gathered by pyrosequencing and cloning directly on clinical samples suggest that the mutant emerged de novo.
RESULTS: During early disease onset, naturally-acquired anti-CHIKV antibodies from patients mostl... more RESULTS: During early disease onset, naturally-acquired anti-CHIKV antibodies from patients mostly target a linear dominant epitope 'E2EP3'located at the N-terminus of the E2 glycoprotein. Up to 80% of anti-CHIKV antibodies are specific against E2EP3 and removal of anti-E2EP3 antibodies partially reversed the neutralizing effects. Sero-positivity of E2EP3 validated across different patient cohorts confirmed that E2EP3 could be a good serology marker for early CHIKV detection.
ABSTRACT Understanding factors associated with de novo daptomycin-nonsusceptible Enterococcus (DN... more ABSTRACT Understanding factors associated with de novo daptomycin-nonsusceptible Enterococcus (DNSE) infections will aid in better understanding the mechanisms of daptomycin nonsusceptibility. We conducted a case-control study to compare patients with DNSE infections who were daptomycin treatment naïve (n= 9) and those with DNSE infections who had exposure to daptomycin (n= 13).
Background Pandemic influenza (H1N1) 2009 is susceptible to oseltamivir. There are few reports on... more Background Pandemic influenza (H1N1) 2009 is susceptible to oseltamivir. There are few reports on its clinical and virologic response to oseltamivir. Methods During the pandemic containment response in Singapore, all patients with positive polymerase chain reaction (PCR) results for pandemic influenza (H1N1) 2009 were hospitalized, given oseltamivir for 5 days, and discharged when daily PCR results for combined nasal and throat swab samples became negative.
Methods We compared CDI rates based on CDTA to ICD-9 codes for all discharges in 2007 from our ho... more Methods We compared CDI rates based on CDTA to ICD-9 codes for all discharges in 2007 from our hospital to determine sensitivity and specificity of ICD-9 codes. Demographic and hospitalization data were analyzed to determine predictors for missing ICD-9 codes. Results During 2007, there were 56,352 discharges. Of these, 268 tested CDTA-positive but only 133 were assigned the CDI ICD-9 code. A total of 141 discharges had the ICD-9 code; 8 were CDTA-negative, the rest were CDTA-positive.
ABSTRACT Understanding factors associated with de novo Daptomycin non-susceptible Enterococcus (D... more ABSTRACT Understanding factors associated with de novo Daptomycin non-susceptible Enterococcus (DNSE) infections will aid in better understanding of the mechanisms of daptomycin non-susceptibility. We conducted a case-control study to compare patients with DNSE infections that were daptomycin treatment naïve (n= 9) and those who had exposure to daptomycin (n= 13).
ABSTRACT Chikungunya is a re-emerging mosquito-borne viral infection that has spread from East Af... more ABSTRACT Chikungunya is a re-emerging mosquito-borne viral infection that has spread from East Africa to Indian Ocean islands and re-emerged in India since 2004. In Malaysia, chikungunya re-emerged after a hiatus of seven years, causing a localised outbreak in a north-western coastal town in 2006 and subsequently widespread outbreaks in 2008. Since the first local outbreak of chikungunya in Singapore in January 2008, chikungunya infections have been increasingly reported in Singapore.
Abstract Introduction: Highly active antiretroviral therapy (HAART) has greatly changed the epide... more Abstract Introduction: Highly active antiretroviral therapy (HAART) has greatly changed the epidemiology of human immunodeficiency virus (HIV) mortality. The aim of this study is to compare the causes of death and factors associated with early death in HIV-infected persons in the pre-and peri-highly active antiretroviral therapy (HAART) periods. Materials and Methods: We conducted a retrospective review of 483 HIV-infected persons who were diagnosed with HIV from 1985 to 2000, and had died within 5 years of the diagnosis.
Uploads
Papers by Angela Chow