The Faculty

Ben Cowling

Professor Benjamin Cowling joined the School of Public Health (SPH) at HKU in 2004. Prior to moving to Hong Kong, he graduated with a PhD in medical statistics at the University of Warwick (UK) in 2003, and spent a year as a postdoc at Imperial College London (UK). Professor Cowling has been the Head of the Division of Epidemiology and Biostatistics since 2013. He is responsible for teaching the introductory module in epidemiology on the MPH curriculum, and is the chairman of the Departmental Research Postgraduate Committee. Professor Cowling is a co-director of the WHO Collaborating Centre for Infectious Disease Epidemiology and Control at HKU SPH.

Professor Cowling’s primary research focus is in infectious disease epidemiology. In recent years he has designed and implemented large field studies of influenza transmission in the community and the effectiveness and impact of control measures. His latest research has focused on the modes of respiratory virus transmission, influenza vaccination effectiveness, and immunity to infections at the individual and population level. He has strong links with China CDC, and the NIGMS-funded Harvard Center for Communicable Disease Dynamics.

Professor Cowling is a fellow of the Royal Statistical Society and a Fellow of the UK Faculty of Public Health. He is the Editor-in-Chief of Influenza and Other Respiratory Viruses, and an Associate Editor of Emerging Infectious Diseases.

He has more than 750 publications listed in Scopus, including 92 articles with 92 or more citations (H-index of 92). Professor Cowling has received numerous awards including HKU Outstanding Young Researcher Award (2011), Croucher Senior Research Fellowship (2015), HKU Outstanding Researcher Award (2017), and RGC Senior Research Fellowship (2020). He was awarded an MBE in Queen Elizabeth II’s 2021 birthday honours.

Rebecca Cox

Rebecca Jane Cox is a Professor of Medical Virology and Head of the Influenza Centre at the University of Bergen and Haukeland University Hospital in Norway, where she leads a team of 18 scientists. She completed her PhD in 1995 at the London Hospital Medical College, University of London, UK, followed by postdoctoral positions at Guy’s Hospital, UK, and the University of Bergen. With over 30 years of experience, Rebecca has played a leading role in international collaborative research on influenza and emerging pathogens. Her work focuses on vaccine development and evaluation, translational immunology, correlates of protection, and pandemic preparedness, with particular emphasis on human clinical trials and cohort studies. She holds advisory roles with major international health organizations, including the WHO, EU, and the European Medicines Agency. Rebecca is also a trustee of the ISRV and serves as Chair of its Education Committee, where she is passionate about training the next generation of scientists. She is also a Senior Editor for the journal Influenza and Other Respiratory Viruses, has authored more than 180 peer-reviewed publications, and regularly contributes to public discussions on respiratory viruses and vaccines through various media platforms.

Vijaykrishna Dhanasekaran

Professor Vijaykrishna Dhanasekaran is a faculty member at the School of Public Health (SPH) at The University of Hong Kong, where he leads the Pathogen Evolution Lab. Prior to joining SPH in 2020, he held faculty positions at Duke-NUS Medical School in Singapore from 2010 and Monash University in Australia, and completed a postdoctoral fellowship in the Department of Microbiology at HKU. Professor Dhanasekaran earned his BSc, MSc, and MPhil from the University of Madras (1994-2000), and his PhD in microbial ecology and evolution from the University of Hong Kong (2002-2005).

His research focuses on the ecology, evolution and epidemiology of rapidly evolving viruses such as SARS-CoV-2, influenza, and RSV. Combining epidemiological studies across the Eurasian and Pacific regions with the integration of genomic, clinical and immunological data, his lab investigates the genetic and ecological factors driving the emergence and distribution of infectious diseases. Professor Dhanasekaran has authored over 150 research articles with more than 16,000 citations (h-index 58). His recent work on the resurgence of highly pathogenic avian influenza (HPAI) H5N1 viruses earned the HKU Research Output Prize 2023-2024. He has also served on the editorial boards of Journal of Virology, Communication Medicine, PLoS Global Public Health.

Julianna Han

Dr. Julianna Han is a structural virologist investigating influenza virus-host interactions using cryo-electron microscopy paired with molecular virology and computational approaches. She leads the influenza research group in Dr. Andrew Ward’s laboratory at The Scripps Research Institute. Her research spans the viral life cycle to antibody-mediated immunity: during her PhD in Dr. Balaji Manicassamy’s laboratory at the University of Chicago, she integrated genome-wide CRISPR screening with mechanistic viral life cycle assays to investigate host factors crucial for influenza infection and probe pan-viral cell-instrinsic immunity. At Scripps Research, her team focuses on two major research areas. First, they structurally map serum polyclonal and monoclonal antibody-epitope interactions from human responses to influenza infection and vaccination, compare these responses across species, and evaluate the effectiveness of immunofocusing in next-generation vaccine designs. Second, they apply structure-guided protein engineering to develop novel immunogen strategies and antibody therapeutics. Together, these efforts leverage advances in influenza immunology, structural biology, and computational protein design to define the immune landscape against seasonal and zoonotic influenza viruses and develop vaccine and therapeutic strategies to strengthen pandemic preparedness.

David Hui

Prof. Hui graduated from the University of New South Wales in 1985. He then trained in Respiratory Medicine and Sleep Medicine in Sydney, Australia.

Prof. Hui was heavily involved in the clinical management of patients with SARS at the Prince of Wales Hospital during the major outbreak in 2003. He served as a WHO advisor to review the clinical management of influenza A(H5N1) during the early human outbreak in Vietnam in Feb 2004 and has since been a regular advisor to the WHO on the clinical management of severe acute respiratory infections. He joined urgent WHO missions for investigation of outbreaks of MERS in Riyadh and South Korea in 2013 and 2015 respectively. He contributed to the WHO treatment guidelines including the clinical management of influenza A (H5N1) virus in 2007, clinical management of influenza A (H1N1) pandemic in 2009, and the Middle East Respiratory Syndrome (MERS) and the WHO training workshop in the clinical management of influenza A(H7N9) and COVID-19. He served as an advisor to the HKSAR government on COVID-19 pandemic from Jan 2020 to May 2023 and has been the Chairman of the Scientific Committee on Emerging & Zoonotic Diseases, Centre for Health Protection, since 2019.

Prof. Hui has published over 500 peer-reviewed journal articles and 24 book chapters since joining the CUHK in 1998. He was the top 1% highly cited researcher (cross fields) from 2021 to 2025 assessed by Clarivate, with H index of 91(Web of Science).

Erik Karlsson

During his doctoral work at, the Department of Nutrition at the Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Dr. Karlsson delved deeply into studying the effect of nutrition on immune responses to viral pathogens – specifically the weight of diet-induced obesity on influenza infection. After completing his Ph.D and being awarded certificates for study in Translational Medicine and Field Epidemiology, he then began pursuing a research career focused on understanding the spread, evolution, and risks of viruses. Karlsson’s postdoctoral and Staff Scientist work took place at St. Jude Childrens’ Research Hospital in Memphis, Tennessee. There he focused on research areas including virology, viral pathogenesis, co-infection dynamics, immunology, and global infectious disease surveillance at animal-human interfaces worldwide. Currently, Dr. Karlsson serves as the Deputy Head of the Virology Unit at the Institut Pasteur du Cambodge (IPC) in Phnom Penh, Cambodia. He is responsible for all ongoing activities related to seasonal and zoonotic respiratory viruses. He serves as Director of the National Influenza Center and Regional WHO H5 Reference Lab, and is Coordinator of a WHO COVID-19 Global Reference Laboratory. His personal work at IPC centres on improving surveillance of endemic and emerging viruses at high-risk interfaces. He utilizes novel surveillance technologies alongside traditional detection and genomic epidemiology methods to enhance Early Warning systems against future pandemics. Aside from his work in research and One Health, Karlsson frequently acts as a technical advisor and consultant for UN organizations like the FAO and WHO on topics such as novel surveillance, biosafety/biosecurity, laboratory development, genomic surveillance, and traditional food markets. He also serves on advisory groups for organizations such as the National Academies of Sciences, Engineering, and Medicine. Recognizing the global nature of pandemic threats at the animal-human-environment interface, Karlsson also founded CANARIES – a research consortium and think tank leveraging animal market networks for enhanced infectious disease surveillance and response.

Ghazi Kayali

Over the past 15 years, Dr. Kayali research has focused on the epidemiology of avian and zoonotic influenza viruses at the human–animal interface, with particular emphasis on the Middle East and Africa. He has led extensive surveillance in live bird markets, commercial poultry farms, and mixed-species production systems to understand how influenza A viruses emerge, persist, and evolve in these high-risk environments. His group has documented sustained circulation of H9N2 and H5 lineages in poultry and mapped their geographic and temporal dynamics across the region. Dr. Kayali has generated critical evidence on cross-species transmission, including the detection of avian and human influenza subtypes in pigs, and recent confirmation of A(H5N1) clade 2.3.4.4b infections in dairy cattle, sheep, and goats in Egypt. He leads one of the few groups globally conducting cohort studies at the human–animal interface, enabling estimation of influenza incidence and seroprevalence among high-risk occupational groups. Beyond field surveillance, he has contributed to influenza vaccine research. As a technical advisor and consultant for the World Health Organization, Dr. Kayali advise on zoonotic disease preparedness, pandemic response, and the implementation of the International Health Regulations. Dr. Kayali currently serves as Managing Partner of Human Link DMCC, a member of the NIH-funded Centers of Excellence for Influenza Research and Response (CEIRR). He remains committed to strengthening One Health surveillance, building local laboratory and field capacities, and advancing integrated, multisectoral systems for pandemic influenza preparedness across Africa and the Middle East.

Nancy Leung

Professor Nancy Leung is an infectious disease epidemiologist with comprehensive training in epidemiology (PhD) and immunology/virology (MPhil), dedicated to understanding respiratory virus infection, immunity, and vaccination. Her research focuses on designing translational epidemiological studies and analyzing combined epidemiological and laboratory data via cross-disciplinary international collaboration to elucidate virus-host interactions and public health policy implications.

She serves as Principal Investigator for several community-based longitudinal observational cohorts, randomized vaccine trials, and household transmission studies involving over 4,000 participants. She is also interested in applying causal inference methods to study vaccine responses.

Prof Leung has written a highly cited review on respiratory virus transmission, and co-chaired or served on two WHO expert groups on SARS-CoV-2 indoor airborne risk assessment (ARIA) and standardizing terminology for pathogen transmission through the air (TTAT). She currently serves as an Editor of the International Journal of Epidemiology (IJE), and an elected Council Member of the International Society for Respiratory Viruses (ISRV).

Professor Leung has taught an introductory epidemiology course at the graduate level (class size 200+), led problem-based learning (PBL) for medical students, and supervised research postgraduates. She strives to promote the integration of epidemiological methods across disciplines, shape global respiratory virus policies, and support LMIC scientists and public health practitioners.

Leo Poon

Professor Poon, a virologist and public health scientist, received his PhD from the Sir William Dunn School of Pathology at the University of Oxford. In 2001, he joined the University of Hong Kong (HKU) as a Research Assistant Professor and is now the Chair Professor in the School of Public Health, also serving as co-director of the HKU-Pasteur Research Pole and co-director of the Hong Kong Jockey Club Global Health Institute (HKJCGHI).

Professor Poon’s research primarily focuses on emerging and re-emerging viruses that threaten human health, including SARS-CoV, SARS-CoV-2, MERS-CoV, and zoonotic influenza viruses. Utilizing the “One Health” concept, he studies viruses at the animal-human interface and has developed molecular tests for various zoonotic viruses. Notably, he contributed to the discovery of the coronavirus responsible for SARS in 2003 and decoded its sequence, leading to the identification of coronaviruses in wildlife, including the first bat coronavirus. During the H1N1 pandemic in 2009, he identified the first reassortant of the pandemic virus in pigs. His work during the COVID-19 pandemic significantly advanced our understanding of SARS-CoV-2 and its public health implications, and he has a strong interest in vaccinology.

Professor Poon has published over 300 peer-reviewed articles and is a founding member of the Hong Kong Young Academy of Sciences. He was awarded a Senior Research Fellowship by the Croucher Foundation in 2017 and has ranked in the top 1% of the world’s most-cited scientists since 2005, with over 45,000 citations and an H-index of 102. In 2023, he received the highly prestigious Louis Pasteur Bicentenary Prize from the Institut Pasteur for his contributions to combating emerging infectious diseases.

Professor Poon serves as an expert for several international organizations, such as WHO, FAO, and WOAH.

Sheena Sullivan

A/Prof Sheena Sullivan is an infectious diseases epidemiologist. She completed her PhD at UCLA in collaboration with the China Centres for Disease Control and Prevention, Beijing. From 2011-2023 she led the epidemiology team at the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne. She is an Adjunct A/Prof with Monash University and the University of Adelaide, collaborating on Australia’s sentinel influenza surveillance. She also consults for the World Health Organization providing advice to member states on the estimation of influenza disease burden, vaccine effectiveness and vaccine impact.

She is a recognised expert on the conduct of observational studies to estimate vaccine effectiveness, especially the test-negative design, and has been invited to speak on the topic at local and international meetings. Her research extends to understanding the mechanisms underlying observations of reduced VE in some groups. She has led or collaborated on small and large sero-epidemiology cohorts to understand the consequences of repeated influenza vaccination, immune imprinting and vaccination in vulnerable groups. She has authored and co-authored over 200 publications in high impact journals such as Lancet Respiratory Medicine, NEJM and NPJ Vaccines and has grants totalling >$6million. She is a council member of the International Society for Respiratory Viruses, Associate Editor for its journal, Influenza and Other Respiratory Viruses, and Associate Editor for the International Journal of Epidemiology

Ryan Thwaites

Dr Ryan Thwaites is an Associate Professor in Respiratory Immunology within the National Heart and Lung Institute, Imperial College London.

Dr Thwaites’ research focuses on the immune system of the human respiratory tract, incorporating studies of natural viral infections and ‘challenge’ studies in healthy adults. These challenge studies include non-infectious human models of innate immune activation (such as Toll-like receptor agonists), allergens and experimental human infection models with respiratory viruses such as Respiratory Syncytial Virus (RSV), influenza, vaccine candidates, and SARS-CoV-2 (the cause of COVID-19). These studies furthered the development of non-invasive techniques for sampling the airways, including the development of nasosorption as a tool for studying respiratory viral infections in children. This work has challenged the existing dogmas of respiratory viral disease severity in children, developed the minimally-invasive endophenotyping of chronic respiratory diseases, and identified the role of neutrophils in governing susceptibility to respiratory viral infections.

During the COVID-19 pandemic Dr Thwaites worked within the ISARIC4C consortium to profile the immunopathogenic response to SARS-CoV-2 infection in cases of severe disease. These studies continued into monitoring the nature and longevity of immunity to SARS-CoV-2 after natural infection and vaccination. These studies sought to identify the elements of the immune response to infection that contributed to disease severity, versus those that contribute to clearing infection.

The Thwaites lab group continues to study the immune response to respiratory viral infections, with particular interests in the drivers of disease severity and the factors governing susceptibility to viral infections.

Tim Tsang

Professor Tim Tsang, Assistant Professor of the Division of Epidemiology and Biostatistics at the University of Hong Kong, obtained his BSc (Mathematics) and MPhil (Mathematics) from The Hong Kong University of Science and Technology, and PhD (Public Health) from The University of Hong Kong. After graduation, he spent three years as a postdoctoral associate in biostatistics at University of Florida.

His research interest is to develop mathematical and statistical methods for infectious disease dynamics and epidemiology. He develops statistical methods to analyze different types of infectious disease data for acute infectious disease such as COVID-19, human and avian influenza, dengue, norovirus and zika. He develops statistical models to perform estimations and simulations for assessment of control measure and public health interventions. Also, he is interested in integrating infectious disease data from different sources to obtain comprehensive insights for infections and transmissions.

Richard Webby

Richard completed his PhD from the University of Otago, New Zealand, before joining St Jude Children’s Research Hospital, Memphis, US. He is currently a Member of the Department of Host Microbe Interactions at St Jude where he has a research program focused on influenza at the human animal interface. He is the Director of the WHO Collaborating Center for Studies on the Ecology of Influenza in animals and the St Jude Center of Excellence for Influenza Research and Response.

Sook San Wong

Professor Wong obtained her PhD in molecular virology, working on dengue virus, from the Department of Microbiology and Immunology at the University of Melbourne, Australia. She subsequently completed her postdoctoral training at the St. Jude Children’s Research Hospital in Memphis, TN, which was also the World Health Organization (WHO) Collaborating Center on the study of the ecology of influenza in lower animals.

Her laboratory’s research interest is focused on understanding the immunological and virological determinants of robust antibody responses after respiratory virus infection and vaccination at a population as well as at the individual level. This includes studying the immunological principles that govern antibody recall of rapidly evolving and antigenically-variable viruses using clinical or human cohort samples, or in animal models. This research area is critical to our understanding of respiratory viruses’ vaccine efficacy and pathogenesis and how that affects the population’s susceptibility to these viruses.

Professor Wong is a full member of the American Society of Virology, American Society of Immunology and a council member of the International Society for Influenza and Other Respiratory Viruses.

Hui-Ling Yen

Professor Hui-Ling Yen received her Ph.D. in Epidemiological Science from The University of Michigan, Ann Arbor followed by her postdoctoral training at St. Jude Children’s Research Hospital, Memphis, TN. Her research interests focus on understanding the mechanisms of influenza transmission among and between different reservoirs, investigating potential virus-host interactions that affect viral pathogenicity and transmission, and examining the molecular determinants that confer antiviral resistance.

A major research focus in her lab has been on transmission mechanisms. The ongoing research projects apply interdisciplinary research tools to study the modes of transmission for influenza and other respiratory viruses under laboratory settings and in the field, including at the animal-human interfaces. Her lab also uses genetic analyses, molecular biology, and phenotypic measurements to study critical molecular determinants and their effect on protein functionality and viral fitness.

Professor Yen is a full member of the American Society of Virology and a committee member of ISRV Antiviral Group. She serves at the Editorial Boards of Antiviral Research and Influenza and Other Respiratory Viruses.

Maria Zambon

Professor Maria Zambon is the current Head of Respiratory Viruses and Director of the National Influenza Centre at the UK Health Security Agency’s (UKHSA) National Reference Laboratory in Colindale, London, UK. With 40 years of experience as a medically qualified influenza virologist – of which three decades have been spent at UKHSA and its predecessor organisations – she has played a crucial role in the surveillance and response to seasonal influenza as well as new and emerging respiratory viruses, both nationally and internationally.

She has been a member of several scientific working groups and advisory committees for UK Government including SAGE (Scientific Advisory Group for Emergencies), NERVTAG (New and Emerging Respiratory Virus Threats Advisory Group), and JCVI (Joint Committee on Vaccination and Immunisation) over many years. Internationally, she is a close collaborator with the World Health Organisation (WHO), representing the UK at global meetings on respiratory virology and providing input into their global influenza surveillance system GISRS.

Her main research interests include the diagnosis of viral infections in humans, especially RNA viruses, the pathogenicity of influenza, and the development of new vaccines for respiratory viruses, particularly influenza. Her PhD on the mechanism of action of amantadine led directly to the identification of a novel class of viral proteins and viral ion channels (influenza M2 protein).

Mark Zanin

Professor Zanin received his PhD in Microbiology from Monash University in Melbourne, Australia and underwent postdoctoral training in influenza virology at St. Jude Children’s Research Hospital in Memphis, TN, USA with Dr Robert Webster and Dr Richard Webby. He subsequently established a research group at the State Key Laboratory of Respiratory Diseases in Guangzhou, China to study the emergence and transmission of zoonotic respiratory viruses. Professor Zanin’s research interests are the host and viral factors underlying transmission of respiratory viruses and interventions against viral respiratory diseases.

Wuji Zhang

Dr Wuji Zhang completed his PhD and postdoctoral training (2020-2025) in Professor Katherine Kedzierska’s Laboratory at the University of Melbourne, at the Peter Doherty Institute for Infection and Immunity. His research focuses on humoral and cellular immune responses to infections and vaccinations of circulating and emerging respiratory viruses.

In 2025, Dr Zhang began as a Research Assistant Professor at the HKU-Pasteur Research Pole, School of Public Health, The University of Hong Kong. Dr Zhang’s laboratory investigates T cell immune responses towards circulating and emerging viruses, including influenza viruses and coronaviruses. His research focuses on the functionality and cross-reactivity of virus-specific T cells in both peripheral blood and the respiratory tract. A key area of interest is understanding the immune responses in vulnerable populations and identifying correlates of broad and robust T cell immunity across various health and disease conditions.

Dr. Zhang’s research efforts have been recognized with several awards, including the Chancellor’s Prize for Excellence in the PhD Thesis (University of Melbourne) and the Chinese Government Award for Outstanding Self-financed Students Abroad (China Scholarship Council).