Surveillance of tuberculosis treatment outcomes of Singapore citizens and permanent residents, 2002-2011.

SETTING: Singapore, which had a tuberculosis (TB) incidence rate of 41 per 100,000 resident population in 2011. OBJECTIVE: To report the outcomes of Singapore citizens and permanent residents treated for TB from 2002 to 2011. METHODS: A computerised treatment surveillance module (TSM) was launched in 2001 to track the progress and outcome of TB patients nationally. Physicians were required to submit an electronic or paper return for every patient at each clinic visit. Treatment adherence, drugs prescribed, treatment delivery mode and final outcome, specified as 'completed treatment', 'lost to follow-up', 'death', 'transferred out', 'permanent cessation of treatment' and 'still on treatment/no final outcome', were captured. Quarterly cohort outcomes at 12-15 months after starting treatment were combined to generate annual treatment outcomes. RESULTS: Treatment completion rates increased from 73.4% to 82.8%. The proportion of patients lost to follow-up decreased from 3.4% to 1.7%, while that of patients still on treatment or with no final outcome decreased from 10.5% to 4.4%. The death rate ranged between 10.2% and 11.7%; the majority were not attributed to TB. CONCLUSION: TB treatment completion among Singapore citizens and permanent residents has improved since 2002 as the likely result of the TSM and other initiatives introduced over the past decade.

Home exposures to environmental tobacco smoke and allergic symptoms among young children in Singapore.

BACKGROUND: Research relating environmental tobacco smoke (ETS) exposures have focused on childhood asthma. There have been fewer studies with conflicting results performed on associations of ETS exposures with allergic symptoms. We are interested to see if ETS exposures in the homes are associated with allergic symptoms among preschool children in Singapore where public smoking is banned. METHODS: A cross-sectional study adopting an expanded and modified ISAAC (International Study on Asthma and Allergies in Childhood) questionnaire for the evaluation of asthma and allergies was conducted on 6,794 children attending 120 randomly selected child care centers. Specific information on demographics and ETS exposures was obtained. Adjusted prevalence ratios (PRs) and 95% confidence intervals (CIs) were determined using Poisson multivariate regression with a log-link function and robust variance estimates as recommended for cross-sectional studies. RESULTS: The response proportion was 70.0%, and 4,759 children from 97 centers participated. After adjusting for covariates, it was found that home ETS exposure was associated with increased risks of current symptoms of rhinitis (PR 1.23; 95% CI 1.01-1.50) and rhinoconjunctivitis (PR 1.79; 95% CI 1.26-2.54). These associations followed dose-response trends with respect to number of cigarettes smoked or smokers in the homes. Home ETS exposures were also associated with higher PRs of wheeze, nocturnal cough and doctor-diagnosed asthma. Compared with paternal smoking, higher risks of the above outcomes were found for maternal smoking. CONCLUSION: Home ETS exposure is a risk factor associated with rhinitis and asthma among preschool children.

The effect of ventilation strategies of child care centers on indoor air quality and respiratory health of children in Singapore.

UNLABELLED: This paper reports the effects of ventilation strategies on indoor air quality (IAQ) and respiratory health of children within 104 child care centers (CCCs) in a hot and humid climate. The CCCs were categorized by ventilation strategies: natural (NV), air-conditioned and mechanically ventilated (ACMV), air-conditioned using split units (AC), and hybrid (NV and AC operated intermittently). The concentration levels of IAQ parameters in NV CCCs are characterized by the influence of the outdoors and good dilution of indoor pollutants. The lower ventilation rates in air-conditioned CCCs result in higher concentrations of occupant-related pollutants but lower outdoor pollutant ingress. This study also revealed lower prevalence for most asthma and allergy, and respiratory symptoms in children attending NV CCCs. In multivariate analyses controlled for the effects of confounders, the risk of current rhinitis among children is significantly higher if they attend mechanically ventilated CCCs compared to NV CCCs. Air-conditioned CCCs were also associated with higher adjusted prevalence ratio of severe phlegm and cough symptoms and lower respiratory illness. Finally, children attending CCCs with hybrid ventilation are at high risk for almost all the respiratory symptoms studied. PRACTICAL IMPLICATIONS: This large field study indicates that different ventilation strategies employed by child care centers can cause significant variations in the indoor air quality and prevalence of asthma, allergies and respiratory symptoms of attending children. The higher prevalence rates of allergic and respiratory symptoms among young children, whose immune system is still under-developed, in child care centers, whether fully or partially air-conditioned, suggest that ventilation and plausible growth and propagation mechanisms of allergens and infectious agents be further investigated.

Oyster-associated outbreaks of Norovirus gastroenteritis in Singapore.

Outbreaks of gastroenteritis associated with the consumption of raw imported half-shelled frozen oysters occurred in Singapore between 16 Dec 2003 and 04 Jan 2004. A total of 305 cases were reported with clinical symptoms of diarrhoea (94%), abdominal cramps (72%), vomiting (69%) and fever (54%). The median incubation period was 30.8h and the duration of illness was 2-3 days. The overall relative risk of oyster consumption was 14.1 (95% CI: 8.3-24.0, P<0.001). Stool and oyster samples tested negative for common bacterial pathogens, including Vibrio parahaemolyticus. However, stool samples were positive for the presence of Norovirus group II RNA via RT PCR while oyster samples indicated the presence of Norovirus particles by electron microscopy. The clinical and epidemiological features were suggestive of Norovirus gastroenteritis and were subsequently confirmed by laboratory tests of stools and implicated oysters. Steps have been taken to ensure that food outlets do not thaw frozen oysters and serve them raw.

Public information and mitigation measures for a haze episode: the Singapore experience

It presents information related to the country-level activities that can be undertaken inrelation to information provision and mitigation measures during a haze emergency. Document in pdf format; Acrobat Reader required.

Epidemiology of sick building syndrome and its associated risk factors in Singapore.

OBJECTIVES: To investigate the occurrence of sick building syndrome in a tropical city, and its relation to indoor air quality and other factors. METHODS: 2856 office workers in 56 randomly selected public and private sector buildings were surveyed. The study consisted of a self administered questionnaire assessing symptoms and perception of the physical and psychosocial environment, inspection of the building plans and premises, and measurement of temperature, relative humidity, respirable particles, chemicals, bioaerosols, and other variables. RESULTS: Symptoms typical of the sick building syndrome were reported in 19.6% of the respondents. Multivariate modelling substantiated contributions associated with low thermal comfort, high work related stress, too much noise, a history of allergy or other medical conditions, poor lighting, young employees, and female sex. Measurements of indoor air quality or ventilation were not found to be reliable predictors of the symptoms. CONCLUSION: The survey confirmed the presence of sick building syndrome and its risk factors in the tropics. A biopsychosocial approach to the problem involving symptomatic treatment, environmental control, good ergonomic design, and stress management is recommended.

Fatal falls from a height: the use of mathematical models to estimate the height of fall from the injuries sustained.

The authors undertook a review of fatal falls from a height, that occurred in 1991-92 in Singapore, with the objective of constructing mathematical models relating the height of fall to the injuries sustained. The 603 cases studied showed a mean age of 41.4 years with a male to female ratio of approximately 2:1. A sub-sample of 416 (69%) of these subjects had fallen from known heights (mean, 26.9 m; range, 3-69.6 m) and were studied in further detail. Bivariate analysis of this group showed that their injury severity score (ISS) was significantly correlated with the height of fall (H) and age (P < 0.01; r = 0.412 and 0.187, respectively). As the ISS is not strictly a continuous variable and varied markedly with H, it was categorised into bands (ISSB) before being subjected to further analysis. Regression modelling to adjust for mutual confounding showed that both height of fall and age were significant independent determinants of the ISSB (P < 0.0001). A model with H as the dependent variable was then constructed to relate the height of fall to ISSB and other statistically significant indicators of the extent and the severity of the injuries sustained. A second model with bands of height (HB) as the dependent variable was similarly constructed to assess the effect of banding both height and ISS. Our findings suggested that the height of fall was significantly associated with age, ISS and the extent of injury (mostly AIS > or = 3), and confirmed the usefulness of these models for investigative purposes. Statistical models could be designed and used to assess any apparent discrepancy between injury severity as determined at autopsy and the suspected/alleged height of fall.

Sick building syndrome: an emerging stress-related disorder?

BACKGROUND: This study examined the role of work-related psychosocial stress in the aetiology of sick building syndrome and tested the hypothesis that in buildings with no recognized environmental problems, health complaints typical of the syndrome were primarily stress-related. METHOD: A case-control study used data from confidential questionnaires to assess symptoms and perception of the physical and psychosocial environment among 2160 subjects in 67 offices. Working conditions were also inspected and indoor air quality monitored. RESULTS: We found an incremental trend in prevalence of sick building syndrome among office workers who reported high levels of physical and mental stress, and decreasing climate of co-operation. This association was confirmed after multivariate adjustment for significant personal and environmental exposure factors. Using a subsample, we further modelled interaction between stress and the other covariates but none achieved statistical significance. CONCLUSION: Our study confirmed stress to be a significant and independent determinant of the health complaints, and that symptoms compatible with the sick building syndrome in many cases were stress-related. Our findings underscore the importance of personal and organizational stress management to prevent ill health at the office.

A shipyard outbreak of salmonellosis traced to contaminated fruits and vegetables.

A large outbreak of food poisoning occurred in September 1996 and involved at least 116 workers at a shipyard in Jurong. Salmonella weltevreden was isolated from the stool specimens of 24 hospitalised cases and three food handlers, giving a total of 27 bacteriologically confirmed cases (25 symptomatic and two asymptomatic) in this outbreak. Based on a case-control analysis, a number of food items consumed on 23 and 24 September 1996 were implicated in the outbreak, viz. a vegetable dish (P < 0.01), watermelon juice (P < 0.01) and cut watermelon (P < 0.001), papaya (P < 0.001) and pineapple (P < 0.05). The median incubation period was 38 hours and the median duration of illness was two days. Four samples of cut fruits obtained from a food stall at the canteen were found to be positive for Salmonella weltevreden. (The antibiogram of all the strains isolated from food samples and stool cultures was similar, consistent with a common source of infection.) Extensive investigation suggested that contamination may have occurred through unauthorised use of industrial water for washing the fresh produce. Early recognition of the outbreak and prompt implementation of control measures prevented further spread of infection.

Local transmission of Plasmodium vivax malaria in Singapore.

A localised outbreak involving 19 cases and two carriers of vivax malaria was reported at Dairy Farm from May to June 1996. Epidemiological investigations showed that the outbreak was caused by the introduction of two foreign workers with imported relapsing vivax malaria into this malaria-receptive area. Transmission of infection occurred amongst 17 other foreign workers residing in the locality and two local residents staying at a condominium nearby. The outbreak was rapidly brought under control through active case finding, isolation and treatment of infected persons, epidemic vector control measures, and improved drainage to prevent Anopheles maculatus breeding. Were it not for the very thorough epidemiological investigations in this episode, foreign workers and local residents with a recent travel history would have been misclassified as imported and the outbreak missed. Medical practitioners should always consider the possibility of malaria in a foreign worker presenting with fever and notify the case as soon as the disease is suspected.

PIP: As a result of both the constant influx of travellers and foreign workers from endemic countries and the presence of Anopheles vectors, Singapore remains vulnerable to malaria. In May and June of 1996, a localized outbreak involving 19 cases of vivax malaria was reported in central Singapore's Dairy Farm area. Resident in this area at the time were 120 foreign workers employed by and living within two nurseries. Following the outbreak, both epidemiologic and entomologic surveillance studies were conducted. The 19 cases of Plasmodium vivax involved 2 local residents of Dairy Farm Estate condominium and 17 foreign nursery workers (1 Thai, 5 Bangladeshi, and 13 Indian). The origin of the outbreak was traced to 2 foreign workers infected with Plasmodium vivax who defaulted on chloroquine treatment and relapsed within 7 months of arrival in Singapore. Malaria symptoms included fever (100%), rigors (94.7%), chills (89.5%), headache (78.9%), and sweating (42.1%). Larvae of Anopheles maculatus were found in 7 habitats: 4 seepages, 1 ground puddle, 1 earth drain, and 1 antimalaria drainage well. Transmission was interrupted within a week after the outbreak was alerted through a comprehensive strategy of active case finding, isolation and treatment of infected persons, epidemic vector control measures, and improved drainage to prevent Anopheles maculatus breeding. Malaria should always be considered in the differential diagnosis of foreign workers who present with fever.

Epidemiological investigations into an outbreak of building-associated illness in Singapore.

In August 1991, the Ministry of the Environment was informed of the occurrence of illnesses suspected to be related to a modern, multi-story office building. Investigations revealed that 34 of the occupants on two floors of the building had non-specific ailments such as eye, throat or skin irritation which caused acute discomfort but resolved upon leaving the premises. Case-control study identified a number of factors significantly associated with the illness; viz. a personal history of allergy, asthma or sinusitis; a high level of work-related stress; and a lack of thermal comfort. One feature of the affected offices was numerous high partitions which tended to obstruct air movement. Adjustments of central temperature to compensate for complaints of "stuffiness" had resulted in wide fluctuations of temperature and relative humidity. Indoor air quality measurements also revealed high bacterial counts, a condition aggravated by the raised relative humidity and inadequate air movement. The problems gradually resolved following major modifications at the offices and air-handling units. This episode confirmed the need for further studies of building-associated illness in the tropics.

Prevalence of varicella-zoster virus infection in Singapore.

The incidence of chickenpox in Singapore has been increasing since 1984. A seroepidemiological survey was conducted in 1989-90 to determine the prevalence of varicella-zoster virus-specific IgG antibody in the healthy population in Singapore aged from 6 months to over 45 years. Overall, 42.8% of 500 samples assayed qualitatively by the ELISA method were positive, with less than one fifth of those aged under 15 years and less than half of the 15-24 year olds possessing antibody to the virus. However, antibody prevalence increased markedly to between 86% and 98% in those over 25 years of age. No significant sex or ethnic difference was noted. The survey confirmed the low herd immunity and the higher susceptibility of the young adult population to varicella infection in a tropical city compared to that of temperate countries.

Biological monitoring of human exposure to environmental lead in Singapore.

An epidemiological survey was conducted in 1990-91 to determine the personal and environmental factors in Singapore which may affect blood lead levels. A total of 1,408 children and adults aged from 6 months to over 50 years were interviewed and their blood samples obtained for analysis using atomic absorption spectroscopy. Overall, the geometric mean blood lead level of the population surveyed was 76.6 micrograms/l. Multivariate analyses revealed that significant variations in blood lead concentrations were related, in decreasing order of importance, to: sex, age, active and passive smoking, exposure to traffic, and exposure to recent paintwork. The consumption of alcohol and traditional medicines were found not to be significant determinants. To reduce the environmental lead problem in Singapore, unleaded petrol has been introduced and control of lead additive in paints is being considered. The national anti-smoking programme should further contribute to an overall reduction in the blood lead level of the population.

Tussockosis: an outbreak of dermatitis caused by tussock moths in Singapore.

An outbreak of acute pruritic rash occurred in March 1990 among 141 residents of a high-rise public housing estate in Bukit Panjang, Singapore. The typical rash consisted of urticarial lesions distributed over the limbs and trunk. The outbreak was associated with a transient increase in tussock moths in the residential estate following an unusual, short dry spell. The aetiology was established when patch tests with crude moth material produced similar eruptions in 5 out of 7 adult volunteers between 40 min and 12 h. Pharmacological experiments with an aqueous extract of moth hairs in isolated guinea pig ileum elicited a response similar to that induced by histamine.

Tussock moth dermatitis: evidence for histamine involvement.

Moth hairs shed by the few tussock moths caught during the first documented outbreak of pruritic dermatitis in Singapore were investigated to provide evidence for the presence of histamine. Aqueous extract of the moth hairs was used for the test and analyses. In the isolated guinea pig ileum, the extract, like histamine, produced responses that were blocked by mepyramine. The high performance liquid chromatographic (HPLC) analysis of the fluorescamine derivative of the moth extract resulted in a fluorescent peak with exactly the same retention. time as the histamine fluorescamine derivative. The mass spectrum of the pentafluoropropionic acid (PFP) derivative of the extract was also identical to that obtained from the reference histamine-PFP derivative. We concluded that histamine was present in the tussock moth hairs and was involved as one of the inflammatory mediators responsible for the pruritic skin rashes.

Acute haemorrhagic conjunctivitis: seroepidemiology of coxsackievirus A24 variant and enterovirus 70 in Singapore.

Epidemics of acute haemorrhagic conjunctivitis caused by a variant of coxsackievirus A24 (CA24v) and enterovirus 70 (EV70) have occurred periodically in Singapore. A seroepidemiological survey conducted before the CA24v epidemic in 1985 and in the midst of the EV70 epidemic in 1983 showed a neutralising antibody prevalence (greater than or equal to 1:4) of 19.1% and 66.9% to CA24v and EV70, respectively. The seropositivity rate to both viruses was highest in children 10-14 years of age, but no sex or ethnic difference was noted. It appears from the data that an epidemic could be triggered when the herd immunity of the population falls below a critical level. There was a significant correlation in seroprevalence between CA24v and EV70 (P = 7.75 x 10(-3).