Background. Medical imaging has played an important role in the diagnosis, progress monitoring and follow-up of most disease entities, in particular chest infections. The emergence of a novel chest disease poses an immediate challenge to the pillars of imaging, namely chest radiography and computed tomography. The characteristic imaging appearances, differential diagnoses and diagnostic pitfalls need to be established for correct diagnosis and appropriate management. The sensitivity and utility of the different imaging modalities will also need to be addressed. / In the event of an outbreak or epidemic, these challenges are made more difficult by an overwhelming number of patients and limited resources. In March 2003, we were faced with such a situation in our institution and the disease was later termed Severe Acute Respiratory Syndrome (SARS). / Patients in Hong Kong were treated with a combination of an antiviral agent and corticosteroids in addition to respiratory support. The majority of patients improved with treatment, although between 20--36% required treatment in an intensive care unit. / Problems and importance. This novel disease of high infectivity, morbidity and mortality posed a major threat to public health and a challenge to health authorities both locally and internationally. With regard to medical imaging, the following research questions were identified: (1) What are the imaging signs of this new disease? (2) Does chest imaging provide a high degree of sensitivity for diagnosing the infection? (3) Are the imaging signs disease-specific or are they similar to other pathology? (4) Does the progressive evolution of the imaging appearance correlate with the clinical status of the patient? (5) Could the imaging appearance be useful for predicting the final outcome? (6) Are there complications that require detection by imaging? / The lung parenchyma is the main site of infection and the resultant microscopic pathology included: pulmonary exudate, sequestration of macrophages, diffuse alveolar damage, proliferation of epithelial cells and hyaline membrane formation. Macroscopic features include alveolar consolidation in the early stages and later, organizing pneumonia or bronchiolitis obliterans organizing pneumonia. / These answers to these questions are essential to our understanding of the disease and to increase our diagnostic ability. (Abstract shortened by UMI.) / This newly emerged disease is a respiratory infection with a high morbidity/mortality and was found to be caused by a coronavirus (SARS CoV). By the end of the outbreak a total of 8098 probable cases of infection were reported worldwide, with a mortality rate of 9.6% (774 deaths). Hong Kong was one of the hardest hit regions, totaling 1755 probable cases of infection and 299 deaths by the end of the outbreak. / Antonio Gregory Ernest. / "September 2005." / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3745. / Thesis (M.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 245-258). / 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. / School code: 1307.

In part ONE of this thesis, including the most up to date information on SARS virology, disease transmission, pathogenesis and laboratory diagnosis will be summarized and presented, including the results of many studies in which I have participated (these references will be underlined as they appear in text). This of course summarizes knowledge that is now known in 2006 but was largely unknown during the initial outbreak. In part TWO, six original clinical studies performed at PWH will be presented: study (1) describes the clinical manifestations and severity of SARS, and its potential to cause major hospital outbreaks; (2) demonstrates the importance of epidemiological linkage in diagnosing SARS; (3) reports the clinical outcomes of a stepwise treatment protocol, which includes the use of corticosteroid therapy as an immunomodulant; (4) demonstrates that corticosteroid therapy can retard viral clearance, and should be used judiciously; (5) demonstrates that a more robust humoral response is associated with severe SARS, thus indicating that passive immunity treatment strategies seem only suitable either during early illness or as prophylaxis; and (6) shows that SARS has few early discriminating laboratory features compared to other causes of community-acquired pneumonia, thus a high index of suspicion is needed to recognize this infection in the absence of worldwide transmission. A thorough review of the relevant published material will be included in the discussion section of each study. / Severe Acute Respiratory Syndrome (SARS) is an emerging infectious disease caused by a novel coronavirus. It caused a global outbreak in 2003, resulting in more than 8000 infections, 700 deaths, and major social and economic disruption. In the initial phase of the SARS outbreak, the medical profession had no knowledge regarding the responsible pathogen, nor the clinical manifestations of SARS and the course of illness. There was no reliable diagnostic tool and no known effective therapy. But for the first time in medical history, we witnessed the rapid accumulation of knowledge on a disease as it evolved, which in turn assisted its management and control. / Since conducting randomized-controlled trials during the 2003 crisis was almost impossible, most of the presented studies are either descriptive or case-controlled in design. However, these studies have laid foundations for recent and future research into the clinical diagnosis and management of SARS. Moreover, the construction of the SARS clinical database has contributed to the work of other investigators, which has resulted in over thirty-six publications. It is my hope that these research endeavors can contribute to the understanding of this emerging, deadly disease. / Lee Lai Shun, Nelson. / "April 2006." / Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0205. / Thesis (M.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 264-292). / 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. / Abstracts in English and Chinese. / School code: 1307.