An unusual outbreak of rotavirus G8P[8] gastroenteritis in adults in an urban community, Singapore, 2016.

BACKGROUND: An outbreak of gastroenteritis (GE) occurred in community-dwelling adults in the Central Region of urban Singapore, in May 2016. OBJECTIVES: To investigate the cause of the outbreak. STUDY DESIGN: We conducted a case-cohort study on GE patients linked to the outbreak who presented to the emergency department of a tertiary-care hospital near the outbreak area, from 18 May to 11 June 2016. Stools were tested for gastrointestinal pathogens including rotavirus antigen and positive rotavirus samples were subject to genotyping. RESULTS: A total of 57 adult GE patients, with a median age of 40 (range 18 to 84) years, were included. Predominant symptoms were diarrhoea (98.2%), vomiting (64.9%), and abdominal discomfort (38.6%). Age 65 years and above (Adjusted OR 21.78, 95% CI 1.49-318.84; P = 0.02) was the only predictor of admission, after adjusting for comorbidities and clinical severity. Molecular microbiological investigations confirmed that the outbreak was caused by a novel human-bovine reassortant strain of rotavirus G8P[8] with DS-1-like backbone. Exposure to the market in the outbreak area was strongly associated with rotavirus infection (OR 46.14; 95% CI 43.04-49.25, P < 0.01). No particular food item could be identified as the outbreak cause. CONCLUSIONS: This is the first report of an outbreak of rotavirus G8P[8] in adults in an urban community that is not waterborne. Transmission was likely through fomites in the market and its surrounding areas, via consumption or contact with contaminated food items purchased from the market, and from person-to-person. The potential for novel G8P[8] strains to cause outbreaks cannot be overemphasized.

Assessing Sensitivity and Specificity of Surveillance Case Definitions for Zika Virus Disease.

We evaluated performance of 5 case definitions for Zika virus disease surveillance in a human cohort during an outbreak in Singapore, August 26-September 5, 2016. Because laboratory tests are largely inaccessible, use of case definitions that include rash as a required clinical feature are useful in identifying this disease.

Review of a two-year methicillin-resistant Staphylococcus aureus screening program and cost-effectiveness analysis in Singapore.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) poses an increasingly large disease and economic burden worldwide. The effectiveness of screening programs in the tropics is poorly understood. The aims of this study are: (i) to analyze the factors affecting MRSA colonization at admission and acquisition during hospitalization and (ii) to evaluate the cost-effectiveness of a screening program which aims to control MRSA incidence during hospitalization. METHODS: We conducted a retrospective case-control study of patients admitted to the Communicable Disease Centre (CDC) in Singapore between Jan 2009 and Dec 2010 when there was an ongoing selective screening and isolation program. Risk factors contributing to MRSA colonization on admission and acquisition during hospital stay were evaluated using a logistic regression model. In addition, a cost-effectiveness analysis was conducted to determine the cost per disability-adjusted life year (DALY) averted due to implementing the screening and isolation program. RESULTS: The average prevalence rate of screened patients at admission and the average acquisition rate at discharge during the study period were 12.1 and 4.8 % respectively. Logistic regression models showed that older age (adjusted odds ratio (OR) 1.03, 95 % CI 1.02-1.04, p < 0.001) and dermatological conditions (adjusted OR 1.49, 95 % CI 1.11-1.20, p = 0.008) were independently associated with an increased risk of MRSA colonization at admission. Age (adjusted OR 1.02, 95 % CI 1.01-1.03, p = 0.002) and length of stay in hospital (adjusted OR 1.04, 95 % CI 1.03-1.06, p < 0.001) were independent factors associated with MRSA acquisition during hospitalization. The screening and isolation program reduced the acquisition rate by 1.6 % and was found to be cost saving. For the whole study period, the program cost US$129,916, while it offset hospitalization costs of US$103,869 and loss of productivity costs of US$50,453 with -400 $/DALY averted. DISCUSSION: This study is the first to our knowledge that evaluates the cost-effectiveness of screening and isolation of MRSA patients in a tropical country. Another unique feature of the analysis is the evaluation of acquisition rates among specific types of patients (dermatological, HIV and infectious disease patients)and the comparison of the cost-effectiveness of screening and isolation between them. CONCLUSIONS: Overall our results indicate high MRSA prevalence that can be cost effectively reduced by selective screening and isolation programs in Singapore.

Clinical and microbiological characteristics of cryptococcosis in Singapore: predominance of Cryptococcus neoformans compared with Cryptococcus gattii.

OBJECTIVES: To describe the clinical features, treatments, outcomes, and subtype prevalence of cryptococcosis in Singapore. METHODS: All patients with laboratory confirmed cryptococcal infections admitted from 1999 to 2007 to a teaching hospital in Singapore were reviewed retrospectively. Identification and molecular types of Cryptococcus neoformans variants and Cryptococcus gattii were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Serotypes were inferred with a multiplex PCR method. RESULTS: Of 62 patients with cryptococcosis, C. neoformans var. grubii was the predominant subtype (in 95%), affecting mainly immunocompromised hosts (91%) with HIV infection (80%). Patients with HIV were younger (median age 36.5 vs. 49.5 years, p=0.006) and less likely to present with an altered mental status (14% vs. 50%, p=0.013). In contrast, delayed treatment (median 7 days vs. 2 days, p=0.03), pulmonary involvement (58% vs. 14%, p=0.03), and initial treatment with fluconazole (25% vs. 2%, p=0.02) were more common in HIV-negative patients. C. gattii was uncommon, affecting only three patients, all of whom were immunocompetent and had disseminated disease with pulmonary and neurological involvement. All C. gattii were RFLP type VG II, serotype B and all C. neoformans var. grubii were RFLP type VN I, serotype A, except for one that was RFLP type VN II. CONCLUSION: C. neoformans var. grubii, subtype VN I, was the predominant subtype in Singapore, infecting younger, mainly immunocompromised hosts with HIV. C. gattii was uncommon, causing pulmonary manifestations in older, immunocompetent patients and were RFLP type VG II.

Rates and predictors for influenza vaccine prescriptions among HIV-infected clinic patients in Singapore.

INTRODUCTION: Although Singapore national guidelines recommend influenza vaccination for individuals with comorbidities, the vaccine uptake remains relatively low. This study examines the rates of influenza vaccine prescriptions in a clinic population, and patient, doctor and clinic factors that could affect the vaccine prescribing rates. MATERIALS AND METHODS: This retrospective review utilised electronic medical records from HIV-infected patients seen in an infectious disease (ID) specialist clinic. Data from 40 randomly selected patients per physician were analysed for the outcome of influenza vaccine prescriptions from 1 January to 31 December 2007. All 7 consultants and the 6 ID registrars who had spent at least 4 months in the Department during 2007 were included. Data analysed included patient, physician, and clinic characteristics, and clinically relevant outcomes of admission within a year, and the length of hospital stay. RESULTS: Of the 461 HIV-infected patients analysed for this study, only 107 (23%) were prescribed influenza vaccine in 2007. Vaccine prescribing rates by individual physicians ranged from 0% to 77%. The outcome of vaccine prescribing was analysed by patient demographics (age >40 years, gender, race), physician characteristics (doctor grade, gender and training), and clinic volumes (number of patients per clinic session). Multivariate analysis demonstrated that patients with female doctors (OR 1.8, 95% CI, 1.1 to 3.0, P = 0.017), and doctors with overseas medical training (OR 11.6, 95% CI, 6.0 to 22.2, P <0.001) were significantly more likely to have influenza vaccine prescribed. On univariate analysis, patients were more likely to be admitted if they were male (OR 2.1, 95% CI, 1.0 to 5.1, P = 0.041), and over 40 years old (OR 2.1, 95% CI, 1.1 to 4.5, P = 0.024). Patients prescribed influenza vaccine showed a non-significant trend for protection against admission (OR 0.7, P = 0.288), and shorter length of stay (median 5 vs 9 days, P = 0.344). CONCLUSION: Influenza vaccine prescribing for HIV-infected outpatients in 2007 was only 23%, even in an ID specialist clinic. There was substantial variability in prescribing rates by individual physicians. Neither patient demographics nor patient volumes per clinic session had an impact on the prescribing rates, but significant predictors included physician gender and medical school training. Patients prescribed influenza vaccine had fewer admissions and shorter hospital lengths of stay, although these trends were non-significant.

Short communication: risk factors for methicillin-resistant Staphylococcus aureus colonization among HIV patients at hospital admission.

Methicillin-resistant Staphylococcus aureus (MRSA) is a nosocomial pathogen that has become increasingly prominent in hospitals and the community. HIV-positive patients may be one of the most MRSA-susceptible populations because of their immunocompromised status. At the Communicable Disease Centre, Tan Tock Seng Hospital, Singapore, we implemented a universal MRSA screening program and performed a case-control study to identify risk factors for MRSA colonization among 294 HIV patients at admission from January 2009 to January 2010. Among 54 HIV-positive patients who were MRSA positive at hospital admission, 16 (29.6%) were positive at the nares/axilla/groin (NAG; one combined swab), 14 (25.9%) were NAG and perianal positive, 3 (5.6%) were NAG and throat positive, 10 (18.5%) were NAG, perianal, and throat positive, 6 (11.1%) were throat positive, and 5 (9.3%) were perianal positive. Upon multivariate analysis, we found that age [odds ratio (OR)=1.04, 95% confidence interval (CI): 1.01-1.07, p=0.006] and CD4 count <200/µl within the past 6 months (OR=4.29, 95% CI: 1.83-10.06, p=0.001) were significant risk factors for MRSA colonization. We generated a receiver operating characteristic curve using these two variables and found that the area under the curve was 0.69, indicating that age and CD4 count <200/µl performed moderately well in discriminating between those with MRSA colonization and those without. The results of our study indicate that HIV patients of older age and reduced CD4 count may have increased risk of MRSA colonization. These risk factors may serve as indicators for cohorting or isolating HIV patients at hospital admission.

Accuracy and user-acceptability of HIV self-testing using an oral fluid-based HIV rapid test.

BACKGROUND: The United States FDA approved an over-the-counter HIV self-test, to facilitate increased HIV testing and earlier linkage to care. We assessed the accuracy of self-testing by untrained participants compared to healthcare worker (HCW) testing, participants' ability to interpret sample results and user-acceptability of self-tests in Singapore. METHODOLOGY/PRINCIPAL FINDINGS: A cross-sectional study, involving 200 known HIV-positive patients and 794 unknown HIV status at-risk participants was conducted. Participants (all without prior self-test experience) performed self-testing guided solely by visual instructions, followed by HCW testing, both using the OraQuick ADVANCE Rapid HIV 1/2 Antibody Test, with both results interpreted by the HCW. To assess ability to interpret results, participants were provided 3 sample results (positive, negative, and invalid) to interpret. Of 192 participants who tested positive on HCW testing, self-testing was positive in 186 (96.9%), negative in 5 (2.6%), and invalid in 1 (0.5%). Of 794 participants who tested negative on HCW testing, self-testing was negative in 791 (99.6%), positive in 1 (0.1%), and invalid in 2 (0.3%). Excluding invalid tests, self-testing had sensitivity of 97.4% (95% CI 95.1% to 99.7%) and specificity of 99.9% (95% CI: 99.6% to 100%). When interpreting results, 96%, 93.1% and 95.2% correctly read the positive, negative and invalid respectively. There were no significant demographic predictors for false negative self-testing or wrongly interpreting positive or invalid sample results as negative. Eighty-seven percent would purchase the kit over-the-counter; 89% preferred to take HIV tests in private. 72.5% and 74.9% felt the need for pre- and post-test counseling respectively. Only 28% would pay at least USD15 for the test. CONCLUSIONS/SIGNIFICANCE: Self-testing was associated with high specificity, and a small but significant number of false negatives. Incorrectly identifying model results as invalid was a major reason for incorrect result interpretation. Survey responses were supportive of making self-testing available.

Causes of death and factors associated with early death among human immunodeficiency virus (HIV)-infected persons in Singapore: pre-highly active antiretroviral therapy (HAART) and Peri-HAART.

INTRODUCTION: Highly active antiretroviral therapy (HAART) has greatly changed the epidemiology of human immunodefi ciency 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. We examined the temporal change in the primary causes of death between those who were diagnosed in the pre-HAART (1985 to 1995) and peri-HAART (1996 to 2000) periods, and compared the demographic and clinical characteristics of the 2 groups. RESULTS: During the peri-HAART period, HIV encephalopathy, cryptococcal meningitis, and lymphoma were no longer the leading causes of death. Opportunistic infections remained important causes of death. Early deaths from the peri-HAART period were older (60 years and above) at diagnosis (Adj OR 7.50; 95% CI, 1.78 to 31.58), more likely to be divorced (Adj OR 5.05, 95% CI, 1.96 to 13.02) and tended to have a low baseline CD4 cell count of <50 cells/ uL (Adj OR 2.18, 95% CI, 1.14 to 4.16) , and were more likely to have received HAART (Adj OR 5.19; 95% CI, 2.22 to 12.12) than early deaths from the pre-HAART period. CONCLUSION: In the peri-HAART era, HIV-infected persons who died within 5 years of diagnosis were those who were older (≥60 years), divorced, or who presented with very late-stage disease (CD4 <50) at diagnosis. More targeted public health interventions, such as targeted public health messages and outreach to increase access to HIV testing and treatment should be developed for these subpopulations.

Surveillance for Clostridium difficile infection: ICD-9 coding has poor sensitivity compared to laboratory diagnosis in hospital patients, Singapore.

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. 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. Community-acquired CDI accounted for only 3.2% of cases. The sensitivity and specificity of ICD-9 codes compared to CDTA were 49.6% and 100% respectively. Concordance between CDTA and ICD-9 codes was 0.649 (p<.001). Comparing concordant patients (CDTA+/ICD9+) to discordant patients (CDTA+/ICD9-), concordant patients were more likely to be over 50 years of age (OR 3.49, 95% CI 1.66-7.34, p = .001) and have shorter time from admission to testing (OR 0.98, 95% CI 0.97-0.99, p = .009). DISCUSSION: Unlike previous studies in the US, ICD-9 codes substantially underestimate CDI in Singapore compared to microbiological data. Older patients with shorter time to testing were less likely to have missing ICD-9 codes.

Influenza B outbreak among influenza-vaccinated welfare home residents in Singapore.

INTRODUCTION: Outbreaks of acute respiratory illness occur commonly in long-term care facilities (LTCF), due to the close proximity of residents. Most influenza outbreak reports have been from temperate countries. This study reports an outbreak of influenza B among a highly immunised resident population in a welfare home in tropical Singapore, and discusses vaccine efficacy and the role of acute respiratory illness surveillance for outbreak prevention and control. MATERIALS AND METHODS: During the period from 16 to 21 March 2007, outbreak investigations and active case finding were carried out among residents and nursing staff at the welfare home. Interviews and medical notes review were conducted to obtain epidemiological and clinical data. Hospitalised patients were tested for respiratory pathogens. Further genetic studies were also carried out on positive respiratory samples. RESULTS: The overall clinical attack rate was 9.4% (17/180) in residents and 6.7% (2/30) in staff. All infected residents and staff had received influenza immunisation. Fifteen residents were hospitalised, with 2 developing severe complications. Genetic sequencing revealed that the outbreak strain had an 8.2% amino acid difference from B/Malaysia/2506/2004, the 2006 southern hemisphere influenza vaccine strain, which the residents and staff had earlier received. CONCLUSIONS: A mismatch between the vaccine and circulating influenza virus strains can result in an outbreak in a highly immunised LTCF resident population. Active surveillance for acute respiratory illness in LTCFs could be implemented for rapid detection of antigenic drift. Enhanced infection control and other preventive measures can then be deployed in a timely manner to mitigate the effect of any outbreaks.

Surgical masks for protection of health care personnel against pandemic novel swine-origin influenza A (H1N1)-2009: results from an observational study.

There is ongoing debate about the efficacy of surgical masks versus N95 respirators for protection against pandemic novel swine-origin influenza A (H1N1)-2009. Our hospital, which is designated to manage outbreaks of emerging infection, has robust surveillance systems to detect infection in staff. The incidence of pandemic H1N1-2009 remained low in staff with use of surgical masks.

Epidemiology of travel-associated pandemic (H1N1) 2009 infection in 116 patients, Singapore.

In June 2009, during Singapore's pandemic influenza plan containment phase, pandemic (H1N1) 2009 was introduced into the country through imported cases. To understand how travel patterns affected the initial outbreak, we examined epidemiologic and travel data for the first 116 case-patients admitted to Tan Tock Seng Hospital, Singapore, with travel-associated infection. Sixty-one percent and 54% of patients, respectively, met US Centers for Disease Control and Prevention and World Health Organization temperature criteria for influenza-like illness. One fourth of the case-patients traveled after illness onset, and 15% became ill while traveling. Regions of exposure for imported infections changed rapidly; case-patients initially arrived from North America, followed by Australasia and Southeast Asia. Case-patients on longer flights were more likely to become ill before arrival; those with shorter flights tended to become ill after arrival. Thermal scanners detected fevers in 12% of the arriving case-patients, resulting in a shorter time to isolation.