A group of American scientists have warned that the coronavirus pandemic "may not be the big one", with fears deadlier viruses are on the horizon and could occur within this generation's lifetime.
The US Army scientists, based in the emerging infectious diseases branch at the Walter Reed Army Institute of Research, have spent the past year finding vaccines and therapeutics to stop not only the "original" strain of Covid-19 but also any new variants.
The director of the branch, Dr Kayvon Modjarrad, told the Defence One 2021 Tech Summit on Monday that the likelihood this generation will see another pandemic during its lifetime is "high".
"We have seen the acceleration of these pathogens and the epidemics that they precipitate."
"And it may not be a coronavirus, this may not be the big one. There may be something that's more transmissible and more deadly ahead of us.
"We have to think more broadly, not just about Covid-19, not just about coronavirus, but all emerging infectious threats coming into the future."
Modjarrad joins a chorus of virologists and infectious diseases experts who, almost since coronavirus first emerged in Wuhan in late 2019, have said it's "inevitable" that other diseases are waiting in the wings, and that humans could play a role in how severe those outbreaks might be and where they'll come from.
Speaking to the Guardian last week, Kirby Institute virologist Professor Stuart Turville said that how much responsibility we take for our impact on the environment could be a defining factor.
"We are clever and unfortunately naive at the same time with respect to the planet.
"Economics and big leaps and bounds in technology bring great standards of living across the globe, but can unearth many unwanted nasties."
While about three-quarters of all novel emerging viral diseases over the past 20 years have been zoonotic (transmitted from an animal source) – most often birds, rodents or bats – missing from discussions of their origins is the role of humans, Turville added.
"Unfortunately, things like climate change and habitat destruction will bring with them 'surprises' as animals struggle to deal with their changing environments courtesy of us."
Medical virologist Professor Dominic Dwyer – a member of the World Health Organisation (WHO) team investigating the origins of the Covid-19 pandemic – agreed, adding that a key part of planning for future pandemics will be understanding animal, environment and human interaction.
"All the viruses that have emerged in the last 50 years have come from either animals or the environment, and the connection, the network, between those factors and humans is so important," he told the Guardian.
"Preparing and planning includes considering demographics, the crowded environments people live in, the healthcare environments that allow some things to spread but not others, climate change and the influence of the way we use the land and interact with wildlife, the way we do trade, farming and tourism.
"All of those things have an impact on what lets a pandemic emerge and get going."
Researcher in viral immunology at Murdoch University, Professor Cassandra Berry, said Australia needs to "start training and investing in its next generation of virus hunters now" in order to respond to future threats more rapidly.
"There are viruses just waiting in the wings. The next pandemic will likely be an airborne virus that's highly transmissible, already out there, highly mutable and with an animal reservoir.
"It will be particularly dangerous if it has no visible signs, if it spreads by stealth.
"We are way overdue for another flu pandemic, and there are ones out there a few mutations away from moving from birds to humans. We need the funding invested now in our researchers to prepare."
Next pandemic 'could be next year'
In March, researchers discovered a series of 24 new coronaviruses in bats in a small region of the Yunnan province, in China's southwest.
"In total, we assembled 24 novel coronavirus genomes from different bat species, including four SARS-CoV-2 like coronaviruses," the team wrote in a report, published in the journal Cell.
One of the 24 – viral sample RpYNO6 – was the closest strain yet to Covid-19, though it had genetic differences on the spike protein, the knoblike structure that the virus uses when attaching to cells, the researchers said.
"Together with the SARS-CoV-2 related virus collected from Thailand in June 2020, these results clearly demonstrate that viruses closely related to SARS-CoV-2 continue to circulate in bat populations, and in some regions might occur at a relatively high frequency," they wrote.
Speaking to NPR, University of Sydney virologist Edward Holmes, who was part of the team, said "we're only just starting to scratch the surface" in terms of how many coronaviruses could be across the world.
"The virusphere of coronaviruses is just immense."
Peter Daszak, who helped lead a 2018 study of how these viruses jump from animals into people and how often they make people sick, said new coronaviruses are constantly jumping from bats and other animals into humans, though the vast majority of "spillover" events don't lead to a pandemic.
"It's happening every day," he said. "I look at the spillover event a bit like rain or snow. These viruses are getting into and trickling across our populations."
Both he and Holmes warned the next coronavirus outbreak could be right around the corner.
"I think we need to face reality here," Holmes said.
"Coronavirus pandemics are not a once in 100 year event. The next one could come at any time. It could come in 50 years or in 10 years. Or it could be next year."