1 Hong Kong Red Cross Blood Transfusion Service, Hong Kong, SAR, China.
2 Public Health Laboratory Centre, Centre for Health Protection, Department of Health, Hong Kong, SAR, China.
3 Department of Pathology, Queen Elizabeth Hospital, Hong Kong, SAR, China.
4 State Key Laboratory for Emerging Infectious Diseases, Carol Yu Centre for Infection, Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong.