The areas that recorded NSW’s first cases of local transmission of COVID-19 have been revealed, as health experts warn this is the measure Australia will need to watch before restrictions can be eased.
Following the initial overseas-acquired cases from China in NSW in January, the first case of local transmission was recorded in Ku-Ring-Gai on February 26, and health authorities were unable to trace the source of infection, new data provided by NSW Health has shown.
By March 1, there were a total of eight overseas-acquired cases recorded in the state and two more locally-transmitted cases – one in Waverley, where the source was unknown, and one in Fairfield that was linked to another known case.
A week later, by March 7, there were a total of 28 locally-transmitted cases and 25 overseas-acquired cases. The source of infection was known for 25 of the 28 locally-transmitted cases.
Early cases outside Sydney included an overseas-acquired case in Armidale recorded on January 30, one in Goulburn on March 5 and one in Mid-Coast on March 6.
Locally-transmitted cases were recorded outside Sydney from mid-March, including early cases in the Central Coast, Cessnock and Lake Macquarie.
By March 24, when an international travel ban was announced and a day after non-essential services were closed, there were a total of 830 overseas-acquired cases and 397 locally-transmitted cases of COVID-19 in NSW, including 97 where the source of infection was not known.
The number of new cases of both locally-transmitted and overseas-acquired infection have gradually fallen since the start of April and, as of Sunday, about 40 per cent of all cases in NSW were acquired locally.
Bryan Rodgers, an honorary professor in the school of demographics at the Australian National University, said a significant proportion of the fall in the number of new daily cases in Australia could be attributed to the decision to stop international travel and requiring arrivals to self-isolate for 14 days.
As overseas-acquired cases were gradually eliminated completely, policies and modelling would need to focus on local transmission, which was unlikely to stop entirely, Professor Rodgers said.
“The efforts of contact tracing, at which we’re doing a really good job and putting in a lot of resources, just drives down your number of community transmission cases,” he said. “You can still have a big epidemic, nobody anticipated the new cases in Tasmania for example, it just happened, one person infected someone else and they infected someone else.
“All you can really do is, when local transmission does happen, do something. Right now, we’ve got such a limit on people moving around that when it does spread you can keep it contained locally.”
Premier Gladys Berejiklian warned earlier this month that social distancing would be the “new normal” until a COVID-19 vaccine was developed.
“Until a vaccine is found, there is no simple way to deal with this issue,” she said.
Professor of public health at the University of Sydney Stephen Leeder said he favoured a “very cautious relaxation of these restrictions” and that it was also important to note the strong local factors in the spread of the virus in different areas.
For example, the proportion of cases that are acquired locally is much higher than the state average of 40 per cent in some local government areas, including Cumberland, where 71 per cent of cases are locally-transmitted; in Liverpool and Ryde, where 65 per cent of cases are locally-transmitted; and in Waverley, where 62 per cent of cases are locally-transmitted.
Professor Rodgers said the potential for an outbreak of locally-transmitted cases would be the main concern over the longer term.
“We know what can happen if one or two people infect a number of people, and then you’re chasing your tail,” he said. “There’s a general idea that everyone’s doing the right thing and most people are, but it doesn’t take many to not do the right thing and that’s the nub of the dilemma.”