For most of his professional life, Associate Professor Sanjaya Senanayake has been studying the potential impacts of pandemics and what their worst-case scenario for society would be.
But as the largest pandemic in more than a century spread across the world, there were still aspects of COVID-19 that one of Australia's most seasoned infectious disease experts didn't expect to see.
"The thing that surprised me was just how global travel facilitated the spread of the virus," he said.
"I knew that it could spread quickly through that, but the rate it did spread really surprised me."
The infectious diseases specialist at the Australian National University has been one of the many epidemiological experts the nation has turned to for expert advice in a year like no other.
The associate professor was one of the leading voices providing advice to governments and organisations on how best to manage COVID-19 and make sense of it, during a time when the profession was relied on more than ever before.
"No single person can be an expert on all things COVID," he said.
"You've got infectious disease experts and physicians and epidemiologists and public health physicians, and we're all contributing in different ways and [providing] knowledge across a range of aspects.
"The importance of good messaging in the media [about the virus] can't be overstated when people were afraid and a lot of misinformation was out there."
Given his line of work, Professor Senanayake said he had seen the potential of a pandemic sometime during the future, but not during his own lifetime.
And while there were many parts of COVID-19 that surprised him, he said the biggest shock wasn't found in Australia.
"If you had told me at the start of the pandemic about the position the US would be in at the moment, I would have been appalled and shocked," he said.
"The [US-based] Centers for Disease Control is an organisation that we in infectious diseases globally look up to, and they have led the way for so many decades.
"Given the US is a rich country, I would have thought they would have been better off."
Australia having been relatively fortunate in the global COVID-19 stakes is a position also shared by fellow ANU infectious diseases expert Dr Peter Collignon.
Dr Collignon has regularly been sought for advice and expert opinion throughout the year when it comes to ways to suppress the virus, and how to keep going about daily life while COVID-19 was circulating through parts of the community.
He said he's been most surprised at how the attitudes of people have shifted during 2020.
"The one basic one that we've often overlooked is people mingling with other people at work while they're sick," Dr Collignon said.
"People have been tolerating others not coming into work any more when they are sick, and not just soldiering on."
The infectious diseases expert first heard about the outbreak of COVID-19 back in January, but said he never foresaw how much the virus would spread internationally and across the Australian community.
"My first thought about coronavirus was that it was an animal-to-person virus and not a person-to-person virus, and that I didn't have to worry about it," he said.
"Internationally, I didn't think it would get to the level that it did.
"However, no one person could have actually predicted how this was going to go."
Despite having spent more than 40 years studying in the field, Dr Collignon said there were still many aspects of the COVID-19 outbreak that surprised him.
Among them was the fact that the spread of COVID-19 among young children was not extensive.
"It was surprising because children are usually big vehicles for viruses, such as measles and the flu," he said.
"Children under 12 were less of an issue compared to their parents."
The infectious diseases expert said another big takeaway from the year had been the approach that one rule for one state doesn't necessarily work in another jurisdiction.
"One of the things I remain concerned about is that people still think it's one extreme or the other: either no worries at all or restrictions everywhere," he said.
"We have got to learn how to have restrictions that are proportionate to the risk."
While many would be hoping for a virus-free 2021, Dr Collignon said it would still be some time before society had rid itself completely of COVID-19, but some of the lessons of 2020 would still come in handy in the months to come.
"One worry is how people have pinned their hope on thinking that drugs will save us," he said.
"However, it is good news how quickly we seem to be making COVID vaccines that are safe and effective."
Professor Senanayake expressed a level of surprise at the speed at which vaccines for a previously unknown disease were able to be produced.
However, he said a speedier approach that would anticipate what kinds of bacteria might cause future outbreaks was needed to create vaccines even faster.
"That would probably cost a lot of money and a lot of trials," Professor Senanayake said.
"But I think if there had been some forward thinking and we had had some some sort of vaccine available back in March instead of December, this would have been a different tale," he said.
