For weeks, Hong Kong's case numbers have stayed low in the single digits every day -- even zero sometimes. People had just begun to let down their guard and resume daily activities, with businesses and public spaces reopening, when the third wave hit -- sending case numbers up to several dozen a day.
Eased restrictions: A high number of local cases don't have epidemiological links to other cases -- meaning "we don’t know how these particular cases have acquired the infection," said Professor Leo Poon, the head of the Division of Public Health Laboratory Science of the University of Hong Kong (HKU).
This suggests that the outbreak was caused by the easing of social distancing measures, Poon said.
The danger is especially high in restaurants when people take off their masks and risk cross-infection, said Ivan Hung, chief of HKU's Infectious Diseases Division.
The virus has mutated: The new mutation means that the virus now multiplies at a higher rate, said Gabriel Leung, Dean of Medicine faculty at the HKU, in an radio interview Sunday.
Both Poon and Hung told CNN that the new mutation, located on the protein responsible for the virus attaching to human cells, makes it “more transmissible.” The mutation has made the new version "fitter than the original virus," Poon said.
A previous study about the mutation found it’s more transmissible, but does not appear to make patients any sicker.
We shouldn't panic: There's still a lot we don't know, said John Nicholls, a clinical professor in pathology at HKU.
For instance, we know the mutation has increased replication in cells by 30% -- but it doesn't necessarily mean the virus is 30% more transmissible. “We need to be cautious about this and do more sequencing to see if the virus in Hong Kong is this ‘mutated’ virus,” Nicholls told CNN.