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

Influenza is a leading cause of respiratory disease worldwide. During pandemic and seasonal influenza, secondary Streptococcus pneumoniae infection is a severe complication that contributes to morbidity and mortality. With the clinical significance of this co-infection, it is imperative to understand the disease mechanisms and how our immune system would be modulated in dealing with the dual infection. First, in vivo co-infection model was established. Mice were sequentially infected with influenza virus and then Streptococcus pneumoniae. Co-infected mice lost their body weight significantly and had 100% mortality, whereas mice infected with either influenza virus or pneumococcus alone lost their body weight transiently and all recovered from the infection. Then, lung inflammatory response during the co-infection was examined. Although it is a common phenomenon that co-infection enhances inflammation, the kinetic of, and the relative contribution of influenza virus or pneumococcus to the lung inflammation is not well defined. Therefore, this study characterized the general lung inflammatory environment after co-infection. It was found that influenza virus and pneumococcus differentially modulated inflammatory response in terms of kinetics, leukocyte infiltration and cytokine production. At the early time point after co-infection, pneumococcal infection contributed more than the influenza virus infection to enhance inflammatory cytokine and neutrophil infiltrating the lung. At the later time point after co-infection, both influenza virus and pneumococcus contributed to synergistically increase inflammatory cytokine and macrophage infiltrating the lung. Influenza virus infection induced IFN-γ that contributed to the elevated IFN-γ level in co-infected mice. Influenza virus and pneumococcus synergistically increased Th2 associated cytokine including IL-4, IL-5, and IL-10. These up-regulated immune responses might contribute to the severe lung pathology. Next, adaptive immunity to co-infection was examined. Literature studying co-infection often reports how prior influenza virus infection impairs the immune response against subsequent bacterial infection. However, whether and how secondary pneumococcal infection would affect the immunity to the initial influenza virus is unknown. Therefore this study investigated the modulation of immunity to influenza virus by secondary pneumococcal infection. It was found that co-infection significantly enhanced virus titer in lung and depleted the number of cell in spleen. Secondary pneumococcal infection after influenza decreased influenza virus specific IgG in the lung and peripheral blood. The reduced level of virus specific IgG was associated with the decrease in the number and the percentage of follicular B cell and CD4 T follicular helper cell through both pneumococcal capsular polysaccharide dependent and independent manner. Treating co-infected mice with immune serum containing influenza virus specific IgG successfully improved survival, which suggested the important protective function of virus specific IgG to the co-infection. Taken together, these data suggested that secondary pneumococcal infection impairs the antibody response to influenza virus, which might enhance mortality after co-infection. In conclusion, this study provides new insight to understand the pathogenesis of co-infection, reveals the general lung inflammatory environment, highlights the negative role of pneumococcus to impair virus control and explores novel treatment for the co-infection. / published_or_final_version / Paediatrics and Adolescent Medicine / Doctoral / Doctor of Philosophy

Objective: Pregnancy has been recognized as a risk factor for severe pandemic influenza illness and this “vulnerable” group is suggested to be heightened alertness to the disease by WHO. This systemic review aims to identify the factors affecting the uptake of influenza vaccination among pregnant women as the immunization uptake among this particular group of population is low or suboptimal worldwide. Methods: Systematic literature reviews were conducted by using MEDLINE and PubMed with the key words: “influenza vaccination uptake” and “pregnant women” in the period of January 2004 to January 2013. It was further supplemented by a manual search for literatures and articles on the WHO website, Centers for Disease Control and Prevention (CDC) website, Google Scholar, and reference lists of reviews captured by initial searches. Results: Of the 222 articles identified, 10 studies were found to be relevant in this system literature review. Influenza vaccine coverage among pregnant women was highly diverse (6.2-76%) among the 10 studies. Overall, pregnant women were more likely to take the vaccination against influenza if they: (1) believed the benefits of the vaccine outweighed the potential barriers, (2) believed the influenza was severe and they were highly susceptible to the disease, and (3) were influenced by the positive cues to action such as recommendation from health care professionals and the experience of the influenza vaccination uptake. Conclusion: Overall, greater emphasis on vaccine effectiveness and safety, and the recommendation from health care providers is needed to increase the number of pregnant women influenza immunization in the future public health campaigns. / published_or_final_version / Medicine / Master / Master of Public Health

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

Although influenza is usually acute self-limiting respiratory infection, influenza viruses are among the most common pathogens that threaten the health of humans and animals worldwide. Various anti-viral therapeutic agents are currently used for treatment and prophylaxis of influenza virus, but the problem is that the targets of these drugs are easily mutated and result in resistance. Therefore, medications that have broad spectrum coverage are urgently needed to combat with the disease. Since nucleoprotein (NP), which is encoded by influenza virus genome, is regarded as a druggable target due to its conserved sequence and important functions during influenza virus life cycle, numerous studies are focused on this protein in attempts to develop broad-spectrum anti-influenza therapeutics. Recently, Kao et al. found that the addition of a novel small molecule nucleozin could lead to large aggregates of NP, which in turn caused cessation of virus replication. Give that the interaction between NP and nucleozin is still not unveiled, it is crucial to identify the binding sites using X-ray crystallography. The full length influenza A/WSN/33 (H1N1) NP gene was cloned into pET28 vector, with His-tag in its C-terminus and overexpressed in E.coli strain Rosetta 2. Cell culture was purified by HisTrap HP and Superdex-200 16/60 gel filtration columns. Crystals were grown using the vapour diffusion method and the NP-nucleozin complex was prepared by soaking native crystal in solution containing 0.25 mM nucleozin for 2h. Crystals of the complex can diffract to 3.0 Å at the Shanghai Synchrotron Radiation Facility. The structure of NP was determined by molecular replacement and it belongs to space group C121 with two NP trimers per asymmetric unit. After further refinement, two nucleozin molecules were found in each asymmetric unit, and each of them could bind with two NP molecules at the same time. The ligand binding pockets were formed by the combination of Y289/N309 pocket from one NP molecule, and R382 pocket from another NP molecule. Therefore, the function of nucleozin is to bridge two NP molecules and lead to NP aggregation, which are in agreement with functional studies on nucleozin. Furthermore, computational models of the NP-nucleozin binding are provided to reveal the mechanism of nucleozin induced aggregation. In addition, recent work on interaction between NP and another novel molecule named compound A has also been briefly described and compared with NP-nucleozin complex at the end of this thesis. Collectively, this study presents a new paradigm for better understanding of how NP and nucleozin interact with each other and hence result in NP aggregates, which is envisaged to accelerate the development of anti-influenza therapeutic agents. / published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

abstract / Microbiology / Master / Master of Philosophy

Despite the World Health Organization identifying pregnant women as the highest priority group for seasonal influenza vaccination, many pregnant women remain unaware of the recommendation and have substantial concerns about the adverse effects of the vaccine on them and their unborn foetuses. Few interventions have been conducted to improve influenza vaccine uptake among pregnant women. Among these studies, the results are inconsistent and the quality is generally low. Brief education has been previously shown to improve women’s health practices during pregnancy. An open-label randomized control trial was conducted to assess the effect of providing brief education on influenza vaccine uptake among pregnant women. A total of 163 unvaccinated pregnant women in at least their second trimester were recruited from antenatal clinics of four public hospitals in Hong Kong. They were randomized to receive standard care or a one-to-one brief education session that provided an overview of the safety and benefits of the vaccine to both pregnant women and their foetuses. Participants were followed up by telephone at two to three weeks postpartum to ascertain vaccination status. The primary study outcome was the influenza vaccine uptake rate and the second study outcomes were the proportion of participants initiating discussion about influenza vaccine with their health care providers, the proportion attempting to be vaccinated, and their knowledge of influenza infection and vaccination. A total of 163 participants were recruited with 155 (95%) participants completing follow-up. The overall influenza vaccine uptake rate was 17.8%. When compared with those receiving standard care, the vaccination rate was higher among participants who received the intervention (23.5% vs. 12.2%; p=0.06). In addition, the increase in the rate of self-initiated discussion with HCPs before and after the intervention was significantly higher in intervention group (26.7% vs. 9.3%; p<0.001) but not in standard care group (13.3% vs. 8%; p=0.481). Among participants who did not receive influenza vaccine, pregnant women in intervention group were substantially more likely to have made an unsuccessful attempt to be vaccinated (39.3% vs. 9.2%; p<0.001). Almost one-third of the pregnant women who had attempted to receive the vaccine (n=13) reported they received advice against vaccination during pregnancy from HCPs. If participants had not been advised against influenza vaccine and were successfully vaccinated, the overall difference in the vaccine uptake rate between the two treatment groups would have been statistically significant (34.6% vs. 18.3%; p=0.02). Brief education can be one strategy to improve vaccination uptake rates among pregnant women. In addition, it is clear from this and other studies that recommendations from HCPs substantially influence vaccination behaviours among pregnant women, both positively and negatively. Therefore, multicomponent approaches should be considered in future vaccination programmes and the synergistic effect of both brief education and HCP recommendations should be further evaluated. / published_or_final_version / Nursing Studies / Master / Master of Philosophy

In the fall of 1918, the First World War was drawing to a close. In the midst of Canada’s first major foray into war since Confederation, another threat became more obvious; influenza. Spanish influenza affected millions of people worldwide from 1918 to 1920 and the Canadian population was not immune to such an outbreak. This thesis uses a Mennonite population and locale, the RM of Hanover, Manitoba, as the focus for a study of influenza. In Hanover, the influenza death rate in 1918 was 13.5 deaths per 1000; double the national Canadian average of 6.1. This thesis examines how structures of healthcare networks in rural communities and tensions between provincial and federal authorities, and the Mennonite population at the end of the First World War contributed to the higher death rate amongst this ethnic group. Influenza in Hanover was a shared experience of influenza amongst a North American Mennonite diaspora. / October 2015

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / abstract / Microbiology / Master / Master of Philosophy