published_or_final_version / Microbiology / Master / Master of Philosophy

published_or_final_version / Pathology / Master / Master of Philosophy

published_or_final_version / Nursing Studies / Master / Master of Nursing

published_or_final_version / Public Health / Master / Master of Public Health

published_or_final_version / Paediatrics and Adolescent Medicine / Doctoral / Doctor of Philosophy

 The emergence of the pandemic H1N1 2009 virus of swine-origin and its transmission back to swine highlighted the need for global surveillance of swine influenza. Serology can help to address the epidemiological situation of influenza infection. Since typical serology tests such as hemagglutination inhibition or microneutralization assays are subtype and partially virus-lineage specific, it is important to select appropriate viral antigens for such studies. A poorly chosen panel of antigens will lead to underestimation of the seroprevalence. The choice of well-matched antigen is difficult if there is no prior virological surveillance in that area and even if there was virological surveillance data, transient infections may go undetected. Hence an universal influenza A type reactive serological test is needed. While such tests are available for poultry, there is little published data on the performance of these commercial influenza ELISA assays for serology on swine sera. In this study we evaluated 3 commercially available competitive ELISA assays, IDEXX? Influenza A Ab test, IDEXX? AI MultiS-Screen Ab Test and IDVet ID Screen? Influenza A Antibody Competition ELISA kit for detecting influenza type A reactive antibodies in swine. The virus antigens and the serum samples were obtained from a 14-year systematic abattoir-based virological and serological surveillance for swine influenza in southern China. The performance was evaluated by ROC curve and scatter plot, together with other statistical parameters including the Youden index to optimize the cut-off levels. Using the optimized cut-off levels, sensitivity and specificity of the IDEXX? Influenza A Ab test was 86% and 89% respectively; for IDEXX? AI MultiS-Screen Ab Test was 91% and 87% and for IDVet ID Screen? Influenza A was 95% and 79%, respectively. These findings help to provide different cut-off levels to maximize the sensitivity or specificity to suit different purposes. We found that the ELISA assay was useful in detecting serum samples that may be positive for influenza antibody but missed in the serology screening tests due to limitations in the chosen antigen panel. The ELISA assay maybe helpful in global swine influenza surveillance programs. / published_or_final_version / Microbiology / Master / Master of Medical Sciences

Background Large outbreaks of influenza are known to occur at correctional institutions such as prisons. Prisoners are particularly vulnerable due to a combination of environmental and socio-behavioural risk factors. Such outbreaks are also challenging to control because of the unique environmental constraints in these institutions. However, no local guidance is available for the prevention and control of influenza outbreaks in correctional institutions. This paper aims to review and synthesise relevant evidence on the topic so that practical recommendations can be offered to the local public health and correctional services. Methods A literature search was performed using PubMed, Google Scholar and Google to locate all relevant articles in English that examined the control of influenza outbreaks at correctional institutions up to May 2012. Findings Eleven studies describing 16 outbreaks of influenza or influenza-like illness at correctional institutions were included in the review. The studies included ten case reports and one case-control study from four countries. The majority of outbreaks took place at prisons. The number of cases in each outbreak ranged from three to over 500. Attack rates were highly variable between outbreaks, while case-fatality ratios were generally low. Control strategies used included social distancing measures, transmission-based precautions, active surveillance and testing, treatment, chemoprophylaxis and vaccination. Nine studies discussed the risk factors for spread and the challenges encountered in the control of the outbreaks. These included agent, host, socio-behavioural, environmental, staff and infrastructural factors. The limited expertise and capacity of correctional institutions in responding to influenza outbreaks should be acknowledged. Close communication and collaboration with public health agencies is called for. To better prepare these institutions to respond to pandemic influenza, a detailed, multidisciplinary response plan should be set up by the various government agencies involved. Conclusions Correctional institutions require the appropriate guidance and support from public health for the successful control of influenza outbreaks. These institutions should be recognised as serving a vital role in the community, and prisoners deserve the same standards of health care that are available to other members of society. / published_or_final_version / Public Health / Master / Master of Public Health

BACKGROUND Influenza is a potential threat to life, economies and security in our globalized world. However, it is still unclear how efficacious non-pharmaceutical interventions are in reducing the virus’ transmission and how the underlying mechanisms of its transmission modes work. Since 2008, numbers of randomized controlled trials (RCTs) regarding the efficacy of hand hygiene interventions in reducing influenza transmission have been published, yet no metaanalysis has ever been performed. Besides, a guinea pig model in 2009 showed that the efficiency of aerosol transmission is adjusted by the ambient temperature and humidity. Therefore, further evidence is needed to confirm the hypothesis. OBJECTIVES To evaluate the efficacy of hand hygiene interventions alone or combined with facemasks in reducing influenza transmission in the community and to investigate the possible roles of latitude, temperature and humidity in relation to the efficacy of the interventions in controlling the spread of influenza. SEARCH METHODS This meta-analysis followed the PRISMA statement. I searched the MEDLINE, PubMed, EMBASE, Cochrane Central Register of Controlled Trials and Cochrane Library databases. SELECTION CRITERIA I included all RCTs assessing the effect of hand hygiene interventions in preventing influenza spread in community settings with clear outcome definitions of laboratory confirmed influenza, clinically diagnosed influenza-like illness (ILI) and their related absenteeism. DATA COLLECTION AND ANALYSIS I ranked the methodological quality of each outcome with GRADEprofiler. I also assessed the heterogeneity across RCTs using I2 statistic and publication bias through visual inspection of Begg’s funnel plots and statistical assessment of regression and rank-correlation. I conducted the meta-analysis with random-effect models and further performed separate analyses for developed and developing countries data in case of a significant level of heterogeneity being noted across the studies. I also incorporated meta-regression to assess the association of latitude, temperature and humidity with the efficacy of hand hygiene interventions. RESULTS I identified 1,593 articles in the initial database search, excluded 1,535, included five from reference lists of review articles, retrieved full articles of 33 and included ten for analysis. The quality of evidence of both laboratory confirmed influenza and ILI were high while that of absenteeism was low. The combination of hand hygiene interventions and facemasks contributed to a significant 45% reduced risk of influenza-related absenteeism in the combined country data while it contributed a significant 23% to a reduced risk of both laboratory confirmed influenza and ILI in developed countries subgroup analysis. The metaregression revealed that the efficacy of the combination of hand hygiene interventions with facemasks increased in a less humid environment. CONCLUSIONS The combination of hand hygiene interventions with facemasks is an effective low-cost intervention to prevent influenza. Further studies to assess the association between humidity and mode of influenza transmission are critically important to support the international guideline on hand hygiene interventions and facemask use. / published_or_final_version / Public Health / Master / Master of Public Health

Backgrounds: Receive seasonal influenza vaccination is the most safe and effective way to prevent seasonal influenza and its complications. According to the WHO, the number of hospitalizations among older people due to influenza could be reduced by a ranged from 25% to 39% as a result of vaccination. It has also been revealed to reduce overall mortality rate of the influenza seasons by a range from 39% to 75%. Moreover, influenza vaccination protects almost 90% healthy adults against clinical disease in industrialized countries, under the precondition that the vaccine antigens and circulating viruses are well matched with each other. However, the prevalence of elderly Chinese people undertaking influenza vaccination is still sub optional, the percentage of which is 62.4%. Previous researches reveal that there are a number of reasons for non-compliance to influenza immunization, including the unfavorable side-effects, doubt to the effectiveness of the vaccine, the fear of needles, as well as unawareness of the seriousness of flu. These are all factors associated with personal willingness. Aims and objectives: The aims of this paper are to explore factors that influence vaccination rate in older people and to examine other countries’ experience to identify useful policies. The specific objectives are: 1. To identify from the published literature factors which contribute either positive or negative impacts on vaccination rates in older people. 2. To group these factors into appropriate categories. 3. To make suggestions on policies to improve vaccination rates based on the identified factors and other countries’ experience. Methods: Relevant publications were achieved through PUBMED. Search strategies as well as criteria for inclusion and exclusion had been predetermined and applied. Analysis includes both community perception factors and interpersonal factors. Results: 17 English literatures were reviewed, revealing predictors of seasonal influenza vaccination for and against, which could be grouped into four categories: Factors relate to demographic, factors relate to Health Belief Model, factors relate to social support, factors relate to advice and information being provided. Conclusion: According to this literature review, demographic factors, factors relate to Health Belief Model, social support and information being provided are revealed to be associated with the elders’ inclination to get influenza vaccination. / published_or_final_version / Public Health / Master / Master of Public Health

Background: The first influenza pandemic in the 21st century, the past 2009 influenza pandemic (pdmH1N1), was caused by a novel H1N1 influenza virus. The virus was first described in April 2009 and is now believed to emerge from re-assortment of bird, pig and human flu viruses. Although this pandemic was relatively mild compared to the past pandemics, better knowledge about its characteristics in transmission dynamics and severity is still of public health interest in order to better prepare for future pandemics. Data: Clinical surveillance data were obtained from eFlu database maintained by Hong Kong Hospital Authority. Information was extracted from all pdmH1N1 virologically confirmed infections (which were all symptomatic) about their dates of symptom onset, and, if applicable, dates of hospitalization, ICU admission and death. Serological data were obtained from various sources: 1) community cross-sectional serological survey; 2) convalescent serological data (from symptomatic and virologically confirmed infections); and 3) serological response kinetics data (from symptomatic and virologically confirmed infections). These serological data combined described serological responses against pdmH1N1 infections in the Hong Kong population from different aspects. Methods: I constructed an age-structured natural history model to mimic the pdmH1N1 transmission dynamics in Hong Kong. The transmission model was linked to hospitalization and serology in order to match the observed data. Based on all the data comprehensively, characteristic transmission parameters (basic reproductive number R0, mean generation time E(Tg), attack rates etc.) in the model were estimated using likelihood-based statistical inferences by Bayesian inference with Markov chain Monte Carlo (MCMC). Results: I estimated that R0 is 1.37 and E(Tg) is 2.16 days, which are both comparable to seasonal flu. Younger age groups <20 years were found to be more susceptible (2.72 times compared to 20-29 age group) to pdmH1N1 infection but older age groups 30-59 years were less susceptible (0.55 times). School closure reduced 0-12 year olds’ within-age-group transmission effectively during the reactive kindergarten and primary school closure from Jun 10 to Jul 9 by 93%. Summer holidays from Jun 10 to Aug 31 also reduced within-group transmission by 65% and 13% for 0-12 and 13-19 years olds respectively. Estimates of infection hospitalization probabilities ranged from 0.2% to 0.9% across age groups. I found that not all infected individuals would have serological response strong enough to be positive in serological test but younger age groups were more likely to have stronger serological response after infection. Conclusions: Clinical surveillance data have been used to estimate the transmission dynamics of pdmH1N1 in 2009. Here, I combined hospitalization surveillance data with serological data collected throughout the first pandemic wave (April to December 2009) from different sources, which could better characterize the transmission dynamics and severity of pdmH1N1 in Hong Kong. Although further validation is needed, serological surveillance should be considered as a supplementary alternative to clinical surveillance in influenza surveillance. / published_or_final_version / Community Medicine / Master / Master of Philosophy