In 1999, Leung joined the
University of Hong Kong (HKU)
Faculty of Medicine (now the
Li Ka Shing Faculty of Medicine) as an assistant professor in the Department of Community Medicine (now part of the School of Public Health), and became an associate professor when the School of Public Health was formed in 2004. During the
SARS outbreak, he established and directed the Infectious Disease Epidemiology Group. He was a Takemi Fellow at
Harvard University from 2004 to 2005, and, after returning to Hong Kong, expanded the Children of 1997 study together with Catherine Mary Schooling, which followed "the majority of all
babies born in
Hong Kong during April and May 1997", during which he led the government's response in the
2009 swine flu H1N1 pandemic. He held the position until 2011 when he was appointed the director of the
Office of the Hong Kong Chief Executive. When his term at the government ended, Leung returned to HKU in 2012 as the head of the Department of Community Medicine until 2013, when the department was incorporated into the School of Public Health, and the inaugural master of
Chi Sun College. During his deanship, the Faculty of Medicine launched the Springboard Scholarships and Second Chance Scholarship schemes to recruit students from more diverse backgrounds. A number of major changes to the faculty took place under Leung's watch, including: • Amalgamation of Departments of
Anatomy,
Biochemistry and
Physiology into the School of
Biomedical Sciences (2015) • Establishment of the
Emergency Medicine Unit (2015) (converted into the Department of Emergency Medicine in 2022) • Expansion of the HKU Health System to include
Gleneagles Hong Kong Hospital as the fourth teaching hospital (2017) • Introduction of enrichment year in the
Bachelor of Medicine and Bachelor of Surgery (MBBS) curriculum (2018), • Establishment of the Jockey Club Centre for Clinical Innovation and Discovery and the Jockey Club Institute of Cancer Care at the redeveloped
Grantham Hospital, supported by a
HKD 1.24 billion donation from the
Hong Kong Jockey Club (expected to open in 2025) • Redevelopment of the Sassoon Road Medical Campus (expected to be completed in 2027). In 2017, it was reported that Leung, together with
Zhang Xiang from the
University of California, Berkeley, were the final two candidates for the next HKU president. The Council of HKU, however, eventually selected Zhang. Leung's tenure as dean was renewed in 2018 for a five-year term until 2023. Leung became the
interim director of the School of Public Health, after the former director,
Keiji Fukuda, retired in 2021. Leung resigned as dean in November 2021 to succeed Leong Cheung at the
Hong Kong Jockey Club as the executive director (charities and community). He joined the Hong Kong Jockey Club on 1 August 2022. Outside HKU, Leung was the founding chair of the Asia Pacific Observatory on Health Systems Policies from 2010 to 2014, an elected council member of the Hong Kong Academy of Medicine from 2012 to 2019, the founding co-director of the
World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control from 2014 to 2018, a member of the
University Grants Committee from 2014 to 2019, and a member of the Youth Development Commission of the
Government of Hong Kong from 2018 to 2022. He is currently serving on the Steering Committee on Primary Healthcare Development of the Government of Hong Kong since 2017, the board of directors of the Laboratory of Data Discovery for Health at the
Hong Kong Science Park since 2020, the board of governors of the
Wellcome Trust since 2021, and the Global Health Risk Framework Commission. During the
COVID-19 pandemic, Leung is one of the experts advising the
chief executive and the
Government of Hong Kong, even after leaving HKU. Academically, Leung was an editor for the
Journal of Public Health between 2008 and 2013, the inaugural co-editor of
Epidemics and an associate editor of
Health Policy. and a member of the editorial advisory board of
The BMJ. Leung is an
ex-officio member of the
Medical and Health Services subsector of the
Election Committee of Hong Kong for the 2021–2026 term. == Research ==