In the past week, Victoria has seen a worrying increase in COVID-19 cases, sparking renewed concerns of a second wave that could disrupt Australia's 'return to normal'.
Most alarmingly, the majority of new cases in Victoria are infections that have been acquired within the community. For some, the source of infection is unknown.
Already, this has led the government to extend their state of emergency for four more weeks until July 19.
So what exactly does this all mean for Victoria?
What is the latest on the outbreak in Victoria?
On Thursday, Victoria recorded 33 new coronavirus cases, the highest daily rise in two months and the ninth consecutive day of double-digit increases.
The spike has seen the state's active cases triple since June 17.
It follows the news on Wednesday that a man in his 80s had died in Victoria from the virus — the first Australian death in a month from COVID-19.
More than 1,000 military personnel have now been called in to help deal with the outbreak, which Premier Daniel Andrews has described as "a public health bushfire".
Premier Daniel Andrews also announced on Thursday they will significantly increase testing in an attempt to quash the outbreak. They are currently processing 18,000 tests a day, but will now actively aim to test 25,000 people a day.
What is a 'second wave'?
As infectious disease experts James Wood and Nic Geard wrote for The Conversation, "When an outbreak is brought under control by social distancing and other measures, it’s possible only a small proportion of the population will have been infected and gained immunity.
"If a population has not achieved herd immunity, enough susceptible people may remain to fuel a second wave if controls are relaxed and infection is reintroduced."
Hence, it's more of a metaphorical term, rather than a medical term, to describe a sustained increase in new cases that occurs after the original surge has slowed down.
If a second wave does occur, experts say it could be just as dangerous.
For example, if we look at the 1918 Spanish flu, there were three waves of the illness during the pandemic. The first wave in the spring wasn’t that bad — it was the second wave in autumn that was the deadliest because it had mutated into a much deadlier version of its former self.
Listen to The Quicky, Mamamia's daily news podcast. On this episode, the team discuss the risk and reality of a COVID-19 second wave in Australia. Post continues below.