Gastroenteritis in the form of diarrhea and vomiting is common in human and is mostly caused by viral infection. As the significant proportion of gastrointestinal infections are still not diagnosed, novel viruses are suggested to be the causative agents of unknown gastroenteritis. Novel and emerging picornaviruses, including human parechovirus (HPeV), Aichi virus (AiV) and salivirus (SalV) are suggested to play an important role in acute gastroenteritis. Since little was known about the molecular and clinical epidemiology of these viruses, the present study aims to investigate the presence of HPeV, AiV and SalV in fecal samples of children with acute gastroenteritis in Hong Kong. Retrospective and prospective studies were performed using fecal samples from pediatric patients hospitalized for acute gastroenteritis from November 2004 to August 2005, August 2006 to October 2006 and September 2012 to August 2013. Among 1708 fecal samples subjected to RT-PCR using primers targeted to 5’NCR of picornaviruses, viruses were detected in 57 samples, with 47 patients (2.8%) positive for HPeVs, three patients (0.18%) positive for AiV and one patient (0.1%) positive for SalV. Phylogenetic analysis of the partial VP1 capsid gene of the 33 HPeV strains revealed the presence of genotypes of HPeV- 1, 3, 4, 5, 7, 10, among which HPeV1 was the predominant genotype circulating in our population. The peak activity of HPeV infection was in autumn. Of the three children with AiV detected in fecal samples, phylogenetic analysis of the partial VP1 and 3CD regions indicated the three AiV strains from fecal samples belonged to the AiV genotype A. Co-detection of different pathogens was noted in 6 samples (10.5%) of 57 stool samples positive for picornaviruses. Among the five samples with HPeV, co-detection with HBoV, AiV, SalV and Aeromonas were observed. In one sample with AiV, picobirnavirus was identified. In conclusion, HPeV, AiV and SalV were found to be present in fecal samples of Hong Kong children with gastroenteritis, with HPeV being the most common virus detected. Routine screening for these viruses in young children with gastroenteritis may better define their epidemiology and help prevent their transmission. / published_or_final_version / Microbiology / Master / Master of Medical Sciences

Norovirus (NoV) is a leading causative agent of non-bacterial gastroenteritis in humans worldwide. NoV is genetically classified into five distinct genogroups in which genogroups I (GI), II, and rarely IV infect humans. Each genogroup is further subdivided into different genotypes. Previous local surveillance studies demonstrated that NoV GII, in particular the genotype 4 (GII/4) strain, is the predominant genogroup circulating in Hong Kong since 2001. Similar epidemiologic observations were also reported in the US, Europe, UK, Australia, and Japan, highlighting the enormous pandemic and epidemic potential of this genogroup. However, explanation for its predominance has been lacking. In this study, we demonstrated that NoV GII, comprised mostly of the GII/4 strain, showed an increased median viral RNA level in fecal specimens which was at least 100-fold higher than that of GI. The high level of viral shedding may confer greater opportunity for transmission of GII strains through the fecal-oral route. We also demonstrated that fecal viral RNA level correlated positively and independently with diarrhea duration in NoV GII/4 infections. The median fecal viral level in patients with protracted (last for ≥4 days) diarrhea was 100-fold higher than that in patients with only limited diarrhea. Longer infectivity period may also confer greater opportunity for virus transmission through the fecal-oral route. Higher chance of transmission may result in more efficient person-to-person transmission and rapid dissemination, maintaining a high level of NoV GII persistence in the community. In summer 2006, a territory-wide gastroenteritis outbreak attributed to NoV has occurred with more than 3,000 cases of laboratory-confirmed NoV infections in Hong Kong. Phylogenetic analysis showed that the virus causing this unprecedented outbreak was a novel NoV GII/4 variant distinct from all previously reported global pandemic and local epidemic strains. In this 2006 variant, we identified two hypervariable regions when compared with previous local epidemic strains in 2005: protruding domain 2 (P2 domain) of viral protein 1 (VP1) and VP1-binding domain of VP2. We mapped frequent amino acid substitutions to the modeled antigenic loop regions of P2 domain. We also identified in carboxyl-terminus of VP1 an epidemiologically important, putative conformational epitope that alternates between two 3-amino acid signatures during pandemic NoV GII/4 strains evolution since 1995. Our findings reflect the rapid evolution of NoV GII/4 under immunological pressure and suggest that immune evasion might be a potential mechanism for pandemic NoV GII/4 strains emergence. Taken together, high level of fecal viral shedding, longer infectivity period, and periodic emergence of novel variant may underlie the global predominance of NoV GII. Further investigations are warranted to better understand the public health and biological importance of NoV GII. / Chan, Chi Wai. / Adviser: Wai K. Leung. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0818. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 124-143). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / School code: 1307.

Background & Objective: Acute gastroenteritis (AG) outbreak in elderly homes is common in Hong Kong, especially during the winter. Although mainly a self-limiting condition, the associated short-term as well as long-term medical and social costs can be extensive. This case-control study aims to investigate the hygienic risk factors related to infectious AG in elderly homes at both institutional and individual levels. Predictor variables under investigation include hand wash practice, infection control practice, routine institutional hygienic practice, food handling practice, and environmental factors such as the home setting, ventilation measures and isolation room setting. / Conclusions: This study found that 'sometimes or never wash hands after toilet' was a significant personal hygienic risk factor for AG transmission. This indicated that toilet may be the most susceptible place and hands are the most susceptible vehicle for AG transmission in Hong Kong elderly homes. A higher percentage of the NOHs had a more frequent routine cleaning practice than the OHs, demonstrating that routine cleaning practice may be an economical and an effective way to prevent AG infection. / Methods: All the elderly homes in the New Territories East were invited to take part in the study. A total of 34 homes and 2,995 residents were recruited in the study sample. The data collection period was from Dec 2007 to May 2009. Cases were notified within one week after a reported AG case, either by a report from the elderly home in question, the weekly check up with the New Territories East Community Geriatric Assessment Teams (NTE CGATs), regular contact with the elderly homes by the research assistant and case referrals from the Accident and Emergency Department from the Prince of Wales Hospital (PWH). One hundred and forty cases and 280 matched controls were recruited. For every AG case reported, two sex and age (within 5 years) and elderly home matched controls were selected. Structured questionnaires were conducted in face-to-face interviews in the elderly homes by trained interviewers. Information about the ventilation and the environmental hygiene of the elderly homes was collected by observation from the research team at the beginning of the study. Descriptive analysis was performed for the characteristics of cases and controls. Multivariate and multilevel logistic regression models were applied and odds ratios (ORs) were calculated for the potential hygienic risk factors. / Results: Multiple conditional logistic regression analysis revealed 'sometimes or never wash hands after toilet' OR:3.09 (95%CI: 1.28 -- 7.42) [ref gp: wash hands every time after toilet] was the major significant risk factor for AG in elderly homes, indicating the possible route of person-to-person transmission. Other significant risk factors included: Self-nutrition evaluation as 'not enough' (OR: 2.07; 95%CI: 1.05 -- 4.06), 'Being hospitalized in past month before the interview' (OR: 2.86; 95%CI: 1.16 -- 7.05), 'Simplified Barthel Index scored <15" (OR: 2.63; 1.06 -- 6.53), and 'Alzheimer's' (OR: 2.75; 95% 1.18 -- 6.40). The institutional hygiene factors were investigated based on the descriptive analysis between the outbreak homes (OHs) and the non-outbreak homes (NOHs). The results indicated that the health worker (HW) to resident ratio was much lower in OHs than NOHs (50% OHs: 1:30-55 vs > 80% NOHs:1:10-29), and a higher percentage of the NOHs had a more frequent routine cleaning practice than the OHs. / Fung, Pui Kwan. / Adviser: Ho Suzanne Sutying. / Source: Dissertation Abstracts International, Volume: 73-02, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 182-206). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.