Via the Sydney Morning Herald: Coronavirus Australia: 'New phenomenon': Why the borders between NSW and Victoria will shut. Excerpt:
The threat of Victoria's community transmission spreading into NSW is what finally led the state government to close the border.
While NSW Premier Gladys Berejiklian had resisted calls for weeks to close the state's borders, she said her stance changed on Monday because the circumstances in Victoria had also changed.
"What is occurring in Victoria has not yet occurred anywhere else in Australia and it's a new part of the pandemic, and as such it requires a new type of response."
On Monday, 10 new cases were confirmed in NSW, all in returned travellers.
In Victoria, Premier Daniel Andrews announced the state had recorded 127 new cases of COVID-19, the highest daily total recorded so far in Victoria.
The state's previous daily record was 111 cases, which was recorded on March 28.
Back then, most new cases were from overseas travellers in hotel quarantine; none of the new cases confirmed on Monday were from overseas travellers.
Associate Professor Adam Kamradt-Scott, an expert in the control of infectious diseases at the Centre for International Security Studies at the University of Sydney, said health authorities wanted to avoid the risk of COVID-19 outbreaks spreading further afield than the current Melbourne hotspots.
"The concern obviously is for the risk that there would be someone who is infected travelling from Victoria into NSW and seeding local outbreaks here," he said.
"That's what the border closures are designed to achieve: reduce risk of importation across state borders, and allow Victorian health authorities to focus on getting a handle and containing the outbreak within Melbourne."
