Dr Mackay said the closure of Australia's borders had potential to flatten the curve "unless we already have widespread community infection". (Australia let 2700 people off the Ruby Princess in Sydney earlier this month releasing of a wave of 133 cased in the community.)
"The biggest threat now in Australia apart from widespread community transmission...is the threat from travellers coming back from outside Australia," Dr Mackay said. "I think Indonesia in particular at the moment is a big risk."
"There are a lot of deaths there but not a lot cases, which means a lot of under-reporting." Dr Mackay also pointed to the Philippines as a risk. "What we don't know yet is how many people are here and spreading before those border closures happened."
According to the Australian Government's Smartraveller website, neither Indonesia nor the Philippines have been added to the list of high risk @COVID19 countries - mainland China, Iran, Italy and Korea. Australians returning from those countries must self-isolate for 14 days. 
However, yesterday, Australian Ambassador to Indonesia Gary Quinlan urged Australian tourists in Bali and in Indonesia more broadly to leave now.
Australian Consul-General in Bali Anthea Griffin tweeted this video message to Australian tourists & expats in Bali and East & West Nusa Tenggara.
From 9pm AEDT 20 March 2020, only Australian citizens, residents and immediate family members can travel to Australia. All travellers to Australia are required to self-isolate for 14 days, either at home or in a hotel.
But as reported by the SMH, planes from Australia to Indonesia are increasingly empty & daily routes home to Australia with airlines including Qantas, Virgin, Garuda, AirAsia, Malindo Air & Jetstar are either hard to find or have been cancelled outright.
Compounding the issue for some travellers was the island-wide shutdown of Bali for the annual observance of Nyepi or Silent Day on Wednesday (Mar 25) when the international airport ceased operations for 24 hours until 6am yesterday & people were without internet for 24 hours.
Yesterday, Bali remained shutdown at the direction of the Bali provincial administraton which ordered that borders between regencies be closed, people should stay in their homes, & the only vehicles allowed to move about were emergency & essential services.
There was internet & people were able to go to the airport but finding transport presented a problem. Grab, Blue Bird Taxis and private vehicles were mostly unavailable. Many drivers went back to their villages for Nyepi & were caught there by the lockdown.
Bali had nine confirned #COVID19 cases as at yesterday (Mar 26) and two deaths. A 53yo British woman became Indonesia's 1st official death from the coronavirus disease when she died in Bali's Sanglah Hospital on March 11. Indonesia reported its first 2 cases only on March 2.
The SMH report said pictures & videos have emerged of tourists [plural] dying on the streets as local hospitals struggle to cope with new cases. As far as I'm aware, only one tourist, a French expat has died on a street in the capital, Denpasar, on Mar 15.
Of the other seven cases confirmed in Bali, four are Indonesian citizens & three are tourists though their nationality has been withheld by the central govt's Director General of Disease Control & Prevention. At least one is a Balinese cruise ship crewman who returned from Italy.
More broadly, Indonesia has 893 confirmed cases based on an offical release of data yesterday, with 78 deaths - eight of them doctors and at least one a nurse. 35 people are said to have recovered. Most cases (515) & deaths (46) have been recorded in the capital, Jakarta.
