As from the 18 August 2020, arrivals at Chek Lap Kok will undergo Wuhan virus testing inside the airport before passing through immigration.
No information has yet been provided from the Centre of Health Protection as to whether those testing positive will be allowed to enter Hong Kong.
For information and personal experiences of the testing procedure and lots of information about quarantining in Hong Kong check out the excellent and informative facebook group: HK Quarantine support group
Note: Information, flight requirements and procedures change regularly so check the CHP website before flying.