Background: Avian influenza is a serious infectious disease attracting great concerns of the world. It not only results in a huge economic loss but also poses a great threat to public health, and poultry production plays a major role of transmission as well as a locus of pathogen evolution, mutation and adaptation of avian influenza virus between wild birds and humans. Therefore, biosecurity measures along the poultry supply chains are important to prevent and control avian influenza. My objective was to summarize the past and present various measures against avian influenza in the industrial, commercial and backyard poultry production systems. Methods: A literature search was performed by PubMed, HKU Scholar Hub and Google. Based on the inclusion criterion and exclusion criterion, the relevant articles were selected with full text in English up to 11st, July 2013. Results: A total of 18 articles were found among the 474 potentially relevant articles. Among these articles, 17articlescame from PubMed and 1 article came from HKU Scholar Hub; 2 articles were closely related to industrial poultry production, 9 articles were closely related to commercial poultry production, 3 articles were closely related to village, rural or backyard poultry production and the rest 4 articles mixed the biosecurity measures in the different poultry production systems. These articles covered various biosecurity measures such as surveillance and monitoring, segregation, cleaning and disinfection, vaccination, training for workers, stamping out, controlling markets and poultry management in the developing and developed countries. Discussion: The common control measures are discussed and the biosecurity is aneffective way to prevent the avian influenza outbreaks in poultry and then to protect the health of all people. However, there were still limitations when implementing biosecurity. Due to local social, cultural, economic, psychological and political factors, it is difficult to prevent and control the avian influenza outbreaks in the poultry supply chains only by one single measure or individual. Therefore, some recommendations referring to cooperation of public and private sectors, comprehensiveness and specifity of measures, improving risk perception and education were discussed. / published_or_final_version / Public Health / Master / Master of Public Health

Objective: To present a systematic review of existing literature that investigates biological plausibility of prenatal hazardous air pollutants’ (HAPs) exposure, in the etiology of autism spectrum disorder (ASD) and related outcomes. Method: Electronic databases Pubmed, Biomed Central and National Database for Autism Research, and grey literature pertaining to air pollution association with ASD and related outcomes were searched using specific keywords. The search included 190 HAPs as defined by The Clean Air Act Amendments of 1990 [U.S.Environmental Protection Agency (EPA) 1994] including air pollutants CO, SO2, NOx, O3 and Particulate Matter (PM). Studies selected for systematic review were assessed on quality and causality. Result: Total of 628 articles from electronic search and 16 articles from grey literature were retrieved. 12 studies that cleared the inclusion and exclusion criteria were systematically reviewed using the PRISMA checklist. Outcomes considered included ASD, Attention Deficit Hyperactivity Disorder, social behavior, social interaction, child behavior, communication, cognitive development, attention problems, mental and psychomotor development, and social competence. Studies were from two countries, United States of America and Spain. Study design was case control and cohort study. Follow up duration for cases ranged from in-utero to less than 9 years. Exposure was measured in ambient air using predictive models and cord blood. Although there were discrepancies in the studies, related to strength of association, analysis and covariates adjusted, the association between air pollution and ASD related outcomes could not be dismissed. Most studies lacked information on blinding when quality was assessed and lacked consistency when assessed on causality, while scored well on temporality and biological plausibility. Discussion: Evidence suggests HAPs are capable of transplacentally affecting cognitive function, especially traffic related pollutants. Study design, sample size, response rate, exposure misclassification, failing to adjusting covariates related to lifestyle, nutrition and other chemical exposures have influenced the estimates and the strength of association. Shortcomings of this review are the English language restriction and single reviewer on study selection process and assessments. Immuno-toxic, neuro-toxic and endocrine disrupting properties of these HAPs necessitates comprehensive prospective studies especially in Hong Kong with the rising prevalence of ASD and ever high reported air pollution indexes. Conclusion: Repeated studies were carried out on the same cohorts and studies were concentrated in U.S.A. On account of a lack of consistency, it is difficult to confirm whether air pollution is a plausible candidate for prenatal exposure in ASD. (Abstract of 391 words) / published_or_final_version / Public Health / Master / Master of Public Health

Background The prevention of chronic diseases has always been a major focus in the medical field as a measure to improve public health. As a potential prevention to one of the most common chronic diseases, vitamin D was previously reported to show some signs of positive effect on the prevention of upper respiratory tract infections. Although trials were performed to demonstrate the association between the effectiveness of vitamin D and upper respiratory tract infections in the past few years, the number of randomized controlled trials was limited. Only one systematic review with meta-analysis was carried out to study the effect of vitamin D supplementation on prevention of respiratory tract infections (Charan et al., 2012). Aim A systematic review of the existing evidence was carried out with the aim to examine the effectiveness of vitamin D supplementation as an intervention in prevention of upper respiratory tract infections. Method Studies were selectively chosen based on the inclusion and exclusion criteria. Retrieval of studies was performed and identified from MEDLINE (Ovid) and PUBMED. MeSH terms of “Vitamin D” and “Upper respiratory tract infections” were applied in the search. Only randomized controlled trials were selected. Non-English publications, reviews, discussions, conference papers, and publications with outcomes being not incidence of URTI, were excluded. The quality of each study was evaluated using the Jadad scale (Jadad et al., 1996). Data from the trials was extracted into the meta-analysis, and odds ratios and confidence intervals were used as measures of the association between vitamin D supplementation and incidence of upper respiratory tract infections across studies. Result Five randomized controlled trials were included in this review. In this meta-analysis, the number of events of upper respiratory tract infections in vitamin D group was lower than that in the placebo group (OR=0.53), suggesting that a 47% lower odds of falling in vitamin D groups than in controls. The 95% confidence interval ranged from 0.30to 0.93and did not include 1, suggesting that the effect of vitamin D on prevention of upper respiratory tract infections was significant. However, when the trials were divided into children and adult groups, the results were significantly different. The result of the trials with two children gave an OR of 0.33(95%CI: 0.13, 0.83), meaning a positive effect of vitamin D could be observed in the vitamin D group, compared to the placebo group. Meanwhile, three trials on adults had an OR of 0.78 (95%CI: 0.56, 1.09), which was insufficient to suggest the two groups were different. Conclusion While the positive effect of vitamin D supplementation for the prevention of upper respiratory tract infections is evident on children in this review, it is much less significant on adults due to inconsistencies in the results. Therefore, more research and trials with improved methodologies would be required in the future to increase our understanding and provide more certainty on this matter. / published_or_final_version / Public Health / Master / Master of Public Health

Objective To investigate whether traffic pollutants have any effect on human cognitive functions and behavior by performing a systematic review on existing research studies. Methods Research articles were identified through four databases – CINAHL Plus, Academic Search Premier and MEDLINE via EBSCOhost and Pubmed using the online electronic resources of the libraries of the Hong Kong University. A total of 119 articles from Pubmed and 86 articles from EBSCOhost were identified, and 72 and 64 studies after limits were applied. The studies used a variety of measures to assess the effects of traffic-related air pollution and cognitive functions and behaviors in both children and adults. Results There were 19 articles in total in the systematic review – 13 on children (aged from 1- 17 years) and six on adults (aged from 26 - 83.5 years). Data were employed from nine different countries. Although there were some discrepancies in the results, there was evidence of the effects of traffic-related air pollution on the brain. Conclusions The causal relationship between traffic-related air pollution and cognitive decline cannot be clearly determined. The systematic review however, generated evidence to support the hypothesis that traffic-related air pollution may affect cognitive development in children, increase risks of behavioral disorders in both children and adults, and increase the rate of cognitive decline in older adults. As a result, this systematic review suggests that the research findings have important implications in the development of public health policy and practice. / published_or_final_version / Public Health / Master / Master of Public Health

Background Epidemiological studies have shown that air pollution was associated with both mortality and morbidity of various diseases including cardiovascular diseases, respiratory diseases and cancers. However, the various traffic-related exposure indicators are difficult to compare due to the diversity of study areas, populations, measures of traffic exposures and confounders. Moreover, most of the studies were conducted in the western and European countries. Few studies using the traffic density as surrogate of traffic-related exposure for effects on mortality risk have been performed in Asia and none has been performed in Hong Kong. Objective This study aims to assess the association between the traffic-related exposure and the all-cause and cause-specific mortality risk in the densely populated city of Hong Kong, where traffic emission plays an important role on the ambient air quality. Methods Three traffic-related indicators were employed including: Road Density (RD) in terms of total length of roads divided by Tertiary Planning Unit (TPU) area; Traffic Density (TD) defined by road lengths times the Annual Average Daily Traffic (AADT) and divided by the TPU area; and Vehicle Density (VD) means average AADT over TPU area. Each exposure was divided into three groups according to tertiles. An ecological study was conducted first with population census and mortality data. The age-sex standardized all-cause and cause-specific mortality rate was calculated for each TPU with the whole Hong Kong death rate in 2010 as the standard. Poisson regression models were performed to estimate risks of traffic-related exposure with adjustment of the marital status, race, education, housing tenure, and median household income. After the TPU-level analyses, a cohort with 64,888 elderly subjects being followed up from 1998 to 2012 was used to assess the association with further control for the individual-level factors including age, sex, education, income, housing, and smoking. The Multilevel Cox proportional regression models were built with adjustment for both the individual level confounders and TPU-level covariates. Excess risks from both models were reported. Results Higher exposure areas were found in the northern part of Hong Kong Islands and the inner city of Kowloon peninsula. Statistically significant association between traffic-related exposure and mortality was observed. For the investigation in the general population, the all-nonaccidental cause mortality was associated with 43% (95% confidence interval 37-48%) and 50% (44-56%) excess risk for areas with the middle and high level TD exposure compared with the low level group. The association was similar with measures of RD and VD. For the cause-specific mortality, the respiratory deaths showed a higher risk when compared with the cardiovascular and cancer deaths. For the elderly subjects, the excess risk of all-nonaccidental causes relative to the low level exposure of 13% (1-26%) and 12% (0-25%) for the middle and high level exposure were smaller when compared with the risk in the general population. Conclusion There is an association between traffic-related exposure and mortality in the general and older population of Hong Kong. In future comprehensive investigations with the individual-level exposure measure are needed. Assessment on the younger population should also be studied. / published_or_final_version / Public Health / Master / Master of Philosophy

Background The consumption of sugar-sweetened beverage (SSBs) among children and adolescents, particularly carbonated soft drinks, are always blamed to be the contributor to the epidemic of overweight and obesity. With the number of obese population increased, people become increasingly more focus on the relationship between SSB and the weight gain problems. However, because there are some characteristics of these beverages that people can get energy and happiness, so that people enjoy drinking sugar-sweetened beverage especially children who like sugar and sweet. So, people are still wondering the association between SSB and obesity. Methods A literature search was performed using Google scholar and Pubmed to locate all relevant articles in English that study the impacts of SSB on the weight gain and obesity on children and adolescent up to December 2013. Findings Eleven core references were found to study the association between SSB and the weight gain among children and adolescent including 4 randomized trial studies, 6 cross-sectional studies and 1 case-control study. Conclusions The data collected from large cross-sectional studies, especially the long-term studies shows that there is a positive association between the intake of SSB and the weight gain and obesity in children and adolescent. A case control study based on hospital shows that the children who with less soft-drink consumptions have lower prevalence of obesity and overweight. In addition, the randomized control trials indicate that the greater consumption of SSB, the easier to gain weights among children and adolescents. Although more evidence are needed, the sufficient evidence exists now are not encouraging the public to intake too many sugar-sweetened beverage as a healthy behavior. / published_or_final_version / Public Health / Master / Master of Public Health

Background Dental caries on primary and permanent teeth is a common chronic disease worldwide with negative effects on children`s quality of life, both in the present and future. Sugar intake is a risk factor for caries. However, the association between sugar-sweetened beverages (SSBs) and dental caries is unclear. Methods A systematic review of relevant literature was performed in PubMed, Cochrane Library and ScienceDirect to locate every journal article in English assessing the association between SSBs and dental caries up to May 2014. Quality assessment criteria were formed by 10 essential items in STROBE statement. Results Fourteen studies were included in the present review, of which 11 were cross-sectional studies and 3 were cohort studies. Study participants were recruited from dentistry units, schools or communities. Interview-based or self-reported questionnaires for parents or caregivers were measurement tools for exposure variables. Clinical/dental examination was used to assess the outcome variables in participating children. Decayed, missing, and filled system was used among studies to record caries status. Sources of potential bias may be measurement on exposure and outcome as well as sources and methods of participants selection. Confounding existed due to nature of observational study and possible confounders included age, gender, education and location of children as well as socioeconomic position and oral health awareness of parents. Synthesis of results suggested that there may be a positive association between SSBs and dental caries, providing evidence for policymaking and recommendations for further studies. Conclusions Sugar-sweetened beverages intake could be considered as positively associated with childhood dental caries. Prevention strategy on individual level and population level on dental caries should put more attention on SSBs. Further experimental studies or research with advanced epidemiological instruments are needed for more confident recommendations on preventive strategies. / published_or_final_version / Public Health / Master / Master of Public Health

Objective Large quantities of epidemiological studies manifest that indoor and outdoor air pollutants may trigger and aggravate asthma symptoms, whose mechanism, however, has not been completely made clear yet. As shown by the result of the experiment in which in-vitro cells and animals are exposed to high-density air pollution, the triggering effect of air pollution on asthma is associated with inflammatory reaction, IgE expression and regulation pathways. However, there is a lack of evidence from population studies to support that association. This study plans to conduct continuous monitoring over indoor and outdoor air pollutants facing the asthmatic children from Beijing with a view to carry out an overall assessment of their exposure to air pollutants. Meanwhile, biomarkers which are directly reflecting airway inflammation as well as the signal molecules which are related to IgE expression and regulation are monitored. The next step is to establish an exposure-effect relationship to explore the trigger effect of air pollutants on childhood asthma. Methods 1. Questionnaires were used to collect general information (including age, drug use, indoor home decoration, passive smoking, diet during the study, indoor mildew, allergic history, history of diseases and family heredity history) in 60 asthmatic children (males, Han nationality, aged 5 to 14 years)from Beijing who were recruited into this study. 2. A comprehensive evaluation was conducted on their exposure levels of air pollutants by continuous monitoring of indoor PM2.5, black carbon, benzene, toluene, xylene and formaldehyde in their houses and collecting monitoring data with respect to PM2.5, PM10, NO2and SO2at air quality monitoring sites near their houses. Benzene, toluene and xylene were measured by two-stage thermal desorption-gas chromatography (GC), formaldehyde by AHMT spectrophotometry, mass concentration of PM2.5by gravimetric method, black carbon in PM2.5by multi-wavelength absorption spectroscopy. The concentration data of ambient outdoor air pollutants were available from the real-time air quality publishing platform of Beijing Municipal Environmental Monitoring Center. 3. Exhaled FeNO of asthmatic children were taken as biomarkers reflecting their airway inflammation. FeNO was measured by electrochemical method (off-line monitoring). 4. Trigger effect of air pollution on IgE signaling pathway of asthmatic children was investigated by determining signal molecules of two signaling pathways related to IgE expression and regulation in peripheral serum. Signal molecules were determined by ELISA. 5. Confounding factors were controlled by stratification analysis and multiple linear regression model, and a comprehensive analysis was conducted of the triggering effect of air pollution on children asthma. Results 1. During the research, as for subjects, concentrations of indoor PM2.5, BC, formaldehyde, benzene, toluene, m-, p-and o-xylenes were 55.3±29.9 μg/m3, 3.8±1.4 μg/m3,62.2±42.7 μg/m3, 13.1±15.9 μg/m3, 18.7±16.7 μg/m3, 7.9±7.9 μg/m3and 3.1±5.0 μg/m3, respectively. The7-day weighted average concentrations of outdoor PM2.5, PM10, SO2and NO2were 101.3±87.6μg/m3, 152.8±88.4μg/m3, 48.6±39.8 μg/m3and 63.1±27.7μg/m3, respectively. There was a significant correlation between 7-day weighted average concentrations of indoor and outdoor PM2.5 simultaneously (r=0.697, P<0.001), with a indoor/outdoor PM2.5concentration ratio (I/O ratio) of 0.86±0.39 (P25-P75ranging from 0.62 to 1.01). 2. After adjusting for such influencing factors as age, types of asthma, and season, analysis of all subjects found that FeNO was significantly positively correlated with either benzene in indoor air, or PM2.5, SO2and NO2 in ambient outdoor air. Separate analysis of subjects untreated with inhaled corticosteroids (ICSs) found that FeNO was significantly positively correlated with PM2.5, SO2and NO2 in ambient outdoor air, while this correlation was not significant in the ICS-treated group. 3. In serum, there was a significantly positive correlation between signal molecules in the two regulatory pathways of IgE expression. After adjusting for such influencing factors as age, types of asthma, and passive smoking. No effect of air pollutants on level of signaling molecule was observed in this study. Conclusion Monitoring results of indoor and outdoor air pollutants show that, at a high level of exposure to air pollutants, exposure of asthmatic children to indoor and outdoor air pollutants may cause or aggravate the airway inflammation. Administration of ICSs can control or attenuate the airway inflammation caused by air pollutants in asthmatic children, while the level of signaling molecule in the regulatory pathway of IgE expression in serum may not be an ideal marker for reflecting the trigger effect of air pollution on children asthma. / published_or_final_version / Public Health / Master / Master of Public Health

The magnitude of noise pollution is fast-growing worldwide. Environmental noise has been linked with several non-auditory health impacts, including annoyance, sleep disturbance, cardiovascular diseases and impaired cognitive performance. Also, environmental noise exposure is associated with increased reported psychological symptoms, prolonged healing time of patients and poorer performance of staff in hospitals. Hong Kong has been suffering from environmental noise for years, especially transportation noise, but lack of relevant local studies to support public health intervention. This review is attempted to summarize three governmental study reports and overseas studies on the relationship between noise and non-auditory effects. Also data on noise complaints will be briefly analysed as a supplement. It is ascertained that noise pollution and noise-induced annoyance and sleep disturbance are prevalent in Hong Kong. Also, noise mapping and subjective auditory effect scales are already available. Noise complaint level in Hong Kong is generally lower than levels in London and New York City, but is probably underestimated. Future studies are needed to emphasize on noise exposure in particular areas and vulnerable populations / published_or_final_version / Public Health / Master / Master of Public Health

Background Insomnia is a common and increasing illness among general population all over the world. With insomnia, patients would more likely to have physical, social dysfunction and mood disorders, and even have increased risk of accidents. Therefore, identifying the harm of insomnia and improving the quality of life of patients are very important. Objectives The objective of this systematic review is to evaluate quality of life in patients affected with insomnia. Particularly focuses on the following two question: 1) How insomnia impact quality of life in patients with insomnia. 2) What factors affect quality of life among people with insomnia, such as demographic factors, physical and psychological factors. Methods Systematic reviewing the articles from 1990 to 2013 in PubMed and Medline, which evaluated the quality of life in patients affected with insomnia, using the keywords “insomnia” AND “quality of life”. Results and Discussion There were 9 articles have been included in this review. The year were ranged from 1998 to 2012,8 out of 9 papers had the average age ranged from 42-57 year old. Insomnia significantly related to all of the eight domains and PCS,MCS of QOL negatively, and both of the severity of insomnia and the number of sleep problems have negative impact on QOL. Moreover, regarding the factors which affect QOL of patients, older, female, not married, smoking, drinking, psychiatric disorders and without treatment were associated with lower QOL. Furthermore, regarding the future directions, in Hong Kong the application of the results in this review is appropriate but still need more studies which evaluating the associated factors of insomniacs’ QOL with validated Chinese version QOL measures. Conclusion There was a negative relationship between insomnia and quality of life, and the severity of insomnia and the number of sleep problems had negative impact on quality of life. Particularly, older, female, single statuse, smoking, drinking, psychiatric disorders had negative influence on patients’s QOL. Regarding the control strategies, using appropriate medical treatment under physician guidance, consultation of mental disorders, increasing the public awareness of the harm of insomnia play a pivotal role in reduce the impairment of insomnia. / published_or_final_version / Public Health / Master / Master of Public Health