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.