Remember to bring enough facemask for your consumption during your trip, majority of the shopping centers, government buildings, hotels & shops will not let you in without you wearing one.
Not really true in HK AFAIK regarding people not allowed into places without face masks. You'll definitely get people stared at you, though...
Crazy thing is that COVID-19 hasnt really affected Hong Kong that bad.
It's completely hammered demand to and from the Mainland.
Yes, a compulsory 14-day quarantine for all travellers arriving from mainland China will do that.
My flight from Guangzhou to HK next month on Cathay Dragon has just been cancelled (not that I was ever going to take it given imposed quarantines in Beijing and HK).
1. Demand to/from mainland was already decreasing prior to the mandatory quarantine. The quarantine does push the demand down to zero, but it's not like the demand was all that high before that, either.
2. There are also outbound restrictions (i.e. other countries restricting entries of HKers) that further hampered CX/KA. Taiwan? Down to 14/wk and soon 4/wk compare to 16-17 daily. Japan? Went to zero now. SE Asia? Had been going down also.
2b. Then there are HKG-US flights. US restricting any non-citizens that had been to mainland = no more people from Shenzhen or rest of PRD coming down to HKG to get on a CX flight = demand reduced as a result. Yes, HKers can go in/out of US with no problems, but there are also only so many HKers that travel to US at a given time.
Not a fun time for CX/KA either way.
tl;dr: Basically CX is hampered in both direction. The situation regarding nCoV in China itself is improving, just in time for the nCoV situation elsewhere to get way uglier.