published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

Our systematic influenza surveillance in southern China revealed that two lineages of H9N2 influenza viruses, represented by Chicken/Beijing/1/94 and Quail/Hong Kong/G1/97, became endemic in the poultry in southern China since 1990’s. These established H9N2 lineages continually evolved to generate many different reassortants (or genotypes) and caused sporadic human infection cases. As co-circulating with H5N1 influenza viruses, the increasing genetic diversity and the capability to cause sporadic human infection make the H9N2 viruses become one of the major candidates with pandemic potential. Even though highly pathogenic H5N1 influenza viruses were seldom detected at the live-poultry markets of Hong Kong since 2002, H9N2 viruses were still commonly isolated in our surveillance program. The accumulated H9N2 isolates provided an opportunity to get insights into the continual evolution of this subtype virus in the region. In present study, we have systematically analyzed the H9N2 influenza viruses isolated from 2005 to 2010. Antigenic and phylogenetic analyses of 60 representative H9N2 viruses showed that the Ck/Bei-like H9N2 virus lineage continued endemic in the terrestrial poultry during the survey period in southern China. Genotyping analyses revealed four prevalent genotypes or reassortant variants in the field. Fifty-three of the viruses analyzed belonged to genotype B14 and B15, which were also the major reassortant variants prevailing in southern China from 2000 to 2005. The remaining seven viruses belonged to novel genotypes that have not been identified before. Our findings suggested that the Ck/Bei-like lineage continually maintained high genetic diversity in this region. The epidemiological findings showed that the isolation rate of H9N2 virus at the marketing poultry in Hong Kong was dramatically dropped down since 2009, which was different from what have observed in other provinces in southern China, but was closely correlated with the hygiene measures implemented in live-poultry markets in Hong Kong, e.g. not keeping live chicken overnight. These findings suggest the proper market policy would directly impact the prevalence of influenza virus in the field. / published_or_final_version / Microbiology / Master / Master of Philosophy

Background Avian influenza A (H5N1) has been circulating around and remains to be one of the major threats to human beings since it first emerged in 1997. Besides vaccines, currently there are two major countermeasures to infection in clinical settings, which are antiviral therapies and immunomodulator treatments. Objectives To summarize evidence on the effectiveness of current treatments against H5N1 infection and to explore the potential benefits of several immunomodulatory agents. Design Systematic review of cross-sectional studies and case series. Data sources Searches of PubMed for articles using the search term “(H5N1[Title]) AND antiviral[Title/Abstract]” and also manual search on PubMed for studies that are cited in some review papers in the first automatic search. Previous search results relating to human H5N1 infection studies are also included. Study selection Included studies that were human H5N1 infection cross-sectional studies or case series in which clinical outcomes were reported, CFR and survival rate were specified or could be easily derived from original data. Results 11 articles met the selection criteria and were included in our analysis. Sample size of the included studies ranged from 8 to 308 lab confirmed cases with median age varied from 10 to 29. Leukopenia, lymphopenia, thrombocytopenia and elevated ALT and AST at admission were strongly associated with worse clinical outcomes with different significance across studies. Oseltmivir treatment was generally initiated earlier among those who survived. Survival benefit of oseltamivir was the most significant if the patient received the treatment within the first two days after symptom onset, and it is still significantly effective when treatment was given up to eight days after symptom onset according to one study we included. Corticosteroid didnot show any beneficial effect or it is associated with a higher risk of death when it is given according to the current treatment protocol and a delayed initiation time. Conclusion Oseltamivir treatment is associated with survival benefit especially when initiated within the first two days after symptom onset, while immunomodulator therapies haven’t shown such benefit so far in clinical setting but some experiments in vitro and in vivo support their use in a manner which is different from the current protocol. / published_or_final_version / Public Health / Master / Master of Public Health

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Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M.A.). / Written for the Dept. of Anthropology. Title from title page of PDF (viewed 2008/03/12). Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 104-117) Also available in print.