It's the coronavirus question on everyone's mind now that Australia and New Zealand has not only flattened the curve but sent it downwards – when will the "second wave" of infections hit?
One Australian infectious diseases expert has rejected the term entirely.
Assistant Vice-Chancellor of the University of Melbourne, Professor Shitij Kapur, led a Covid-19 webinar held by the Australian Academy of Health and Medical science this week.
"The question which is top of mind for people is – Given where Australia [and NZ] is today, what are the kinds of infection numbers which will tell you that there is a second wave coming?" he asked.
Associate Professor Kamalini Lokuge, a public health physician and medical epidemiologist working at the Australian National University, was quick to respond.
"I think this term second wave comes from the Spanish flu outbreak and I don't like it at all, because it was waves of transmission across the whole community," she said.
The Spanish flu pandemic, considered "the mother of all pandemics", caused approximately 50 million deaths worldwide from 1918 to 1919.
The virus infected about a third of the Earth's population at the time, or 500 million people.
In mid-April, Singapore recorded its biggest single-day jump in numbers since the Covid-19 pandemic began in China and spread.
It had previously been considered a global success story alongside South Korea for its response to the coronavirus outbreak.
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On Tuesday, 511 of Singapore's 528 news cases detected were migrant workers living in cramped dormitories.
Pandemic expert Richard Coker, the former head of an infectious diseases program at the National University of Singapore, told MarketWatch the country's migrant populations are "somewhat invisible and perhaps forgotten".
Prof Lokuge said: "People are calling what's happening in Singapore a second wave.
"What is happening in Singapore is people who had no access to welfare, no access to money to buy food, who were living 20-to-a-room in hostels and who had no access to healthcare, had unrecognised transmission of the disease for an extended period.
"Now that is not a second wave, that's a poor management of a high-risk population so I would say, and if you look at the breaks in many settings of Covid-19, it's exactly the same.
"Going back to what would tell us that we have control of this disease, is everybody who needs to be tested coming forward to be tested, so I don't want to talk about numbers, that's what I will say.
"I think we can get there very quickly in terms of a really effective surveillance system."
Prof Kapur said the infectious diseases expert's message was an "important one".
"It might actually be counter-productive to focus on a number when we really need to focus on the strength of the system and its ability to respond," he said.
On Wednesday, deputy chief medical officer Professor Paul Kelly was asked about the risk of a second wave of infections in Australia as winter looms and restrictions are eased.
"As we've seen in some other countries like Germany and Singapore", the journalist added.
Prof Kelly said a second wave "is always possible".
"That's why those three precedents have been set by the Prime Minister before we lift those social distancing and social isolation rules about case finding, keeping the cases low if possible, if cases occur, finding them quickly, finding their contacts, quarantining them and decreasing the size of any outbreaks that we might have by having a very detailed and quick response," he said.
"So if a second wave does occur we'll know about it quickly and we'll respond to it.
"Of course we're always looking for a vaccine to be developed, that will be some time away but that would be the way to guard against a second wave completely."
Prof Kelly noted herd immunity is "one way of guarding against a second wave", which some countries planned to do or were forced into due to large caseloads, but that approach is "definitely not" being considered in Australia, or New Zealand.
About 60 per cent of the population of Australia, or 15 million people, would need to be infected for such a strategy to work.
Prof Kelly said he was sure "the second wave" would be a topic for quite some time.
"In one sense, we're victims of our success there to an extent," he said.
"Because we've had so few people that have been diagnosed with Covid-19, and we are nowhere near that concept of herd immunity."
Prof Kelly was also asked whether the second wave is often "harder to fight" than the first wave of infections.
"Not necessarily," Prof Kelly said.
"So thinking of the 1918–19 flu pandemic just after the First World War, there were a lot of reasons why that second wave was worse, which I don't think pertain to now.
"We are very prepared, much better prepared than we were then, in relation to what might happen in a second wave.
"And certainly that ability to do the laboratory testing as I said, rapidly and accurately, to be able to find cases, find their contacts, another reason to download the app, will really help us to fight a second wave.
"And I'm sure that there are many clinical trials going on with various treatments at the moment. So by the time — the longer we leave that second wave into the future the more likely it is we'll have successful treatments."
Australian prime minister Scott Morrison has flagged a national cabinet meeting with state and territory leaders in mid-May, saying it will be crucial to lifting some social and economic clamps that have hogtied the nation.
He said "of course" there will be outbreaks, but "that is what living with the virus will be like".
Morrison also said restrictions can be eased as large-scale surveillance testing can catch sleeper cases and detect any spread that might indicate a second wave has begun.
On Monday, the World Health Organisation said the relaxation of restrictions "must still be complemented by hygiene measures, physical distancing and community participation", while on the public health side, "surveillance, case finding, contact tracing and quarantining will continue to be essential".
"The second wave is in our hands," WHO director-general Dr Tedros Adhanom Ghebreyesus said.