They took their time - even now it's not because of the risk of importing more of the virus into Australia, it's only because the US and Singapore wouldn't allow Qantas crew to fly to their countries if Qantas was still flying to China.
Note as well they're calling this an "Update on China Services", trying to downplay the fact they'll stop flying in the Chinese market.
Qantas will suspend its two direct services to mainland China (Sydney-Beijing and Sydney-Shanghai) from 9 February until 29 March 2020.
This follows entry restrictions imposed by countries including Singapore and the United States, which impact the movement of crew who work across the Qantas International network.
These entry restrictions pose significant logistical challenges for rostering crew to operate mainland China services, leading to the need to temporarily suspend these flights.
There is no change to Qantas services to Hong Kong as it’s exempt from current travel restrictions.
In selecting a date to suspend services Qantas is working to balance high passenger numbers in both directions – including Australian residents wanting to return home from China – with the various travel restrictions being applied. The suspension may be brought forward if demand levels or other factors change. The date for flights to resume will also be regularly reviewed based on the circumstances.
Qantas is liaising closely with the Australian Government on the impact of these changes to citizens currently in mainland China, and continues to take advice from the World Health Organisation and Australia’s Chief Medical Officer regarding the Coronavirus in its decision-making.
Qantas thanks customers for their understanding and its crew for their professionalism in light of these ongoing developments.
Customers with bookings between 9 February and 29 March will be contacted by Qantas to discuss options. There is no change to Qantas codeshare arrangements on China Eastern and China Southern flights.
 As previously announced, Qantas’ Sydney-Beijing service was scheduled to end on 23 February 2020 for commercial reasons. With this announcement, it will now end on 9 February instead.