SARS, MERS, COVID-19 and Disease X? Another pandemic may still be ahead of us. But what could it be? – ABC News

While we may be looking forward to the end of thecoronavirus crisis, health experts warn there may be more pandemics ahead of us.

Within the last 20 years alone, we've"dodged five bullets" withSARS, MERS, Ebola, avian influenza and swine flu.

But despite the knowledge gained from those experiences, we were still largely unprepared for thecoronavirus crisis. And the speed of its spread highlightsthe dangers posed by a hyper globalised world in a pandemic.

With more signs that things are ramping up, senior health officials from the World Health Organization warned last year thatalthough the coronavirus pandemic has been "very severe,"it is "not necessarily the big one".

While many years ago, a disease might have emerged in one area of the world and then have "died out before it spread anywhere else having global trade and travel means that the disease finds new human hosts really quickly," says Victoria Brookes, a senior lecturer in population health at Charles Sturt University.

AP:Emilio Morenatti

Globalisation has also caused profound changes in the conditions that help shape infectious diseases, particularly those that originate in wildlife.

As our population increases, cities are encroaching further and further on wildlife habitats, disrupting living patternsand causing stress to animals.

As ecosystems are destroyed, animals are broughtintocloser contact with humans due to environmental degradation and deforestation, becoming a key driver of "spillover events".

These incidents occur when a virus mutates enough times to allow it to jump to another species and requires close contact between the host species and the species it's moving into. It is believed a spillover event is what sparked the coronavirus pandemic.

"One of the strongest drivers for the emergence of new diseases is the increased interaction between humans and animals,"Hassan Vally fromLa Trobe University'sDepartment of Public Health said, pointing to urbanisation, environmental degradation and deforestation as bringing animals in closer contact with humans.

"Climate change is another driver for the emergence of new diseases.

"These drivers combined with the fact that if a pathogen with pandemic potential does emerge, it can spread quickly due the highly mobile nature of people in the modern world, further exacerbates the risk these diseases pose."

It is estimated that more than 60 per cent of emerging infectious diseases are zoonoses.It's why researchers are particularly focused on the crossover between humans and wildlife.

"The populations that we expect to see these arising fromaremore likely to be species that live in large colonies, thattravel long distances," Dr Brookes said.

"They mix with other populations of the samespecies and also, because they fly, they have contact with lots of other species, [as well as] people."

Zoonosesare caused by the transmission of pathogens such as viruses, parasites, bacteria or fungi either by direct contact or indirect contact between animals and people. This can be through the environment with the help of vectors or carriers.

Reuters:Ueslei Marcelino

It's believed there are just over 250 known zoonotic virusesviruses that have previously spilled over from animals to humans and caused disease in people.

But while these viruses are of ongoing concern, it isthe yet to be identified viruses that "pose an equal if not more serious threat to humanitystudy" according the authors behind a research paper on ranking the risk of animal-to-human spillover for newly discovered viruses.

The WHO has even given this unknown threatits own classification:Disease X, and listed it alongside Ebola and SARS as a top priority for research.

We have no idea what it is or what it can do. But scientists argue without adequate surveillance and preparedness we are doomed to wait for Disease X to emerge.

Before COVID-19, there was the severe acute respiratory syndrome (SARS-CoV-1) in 2003, Middle East respiratory syndrome (MERS) in 2013, and the Ebola virus disease in 2014.

Reuters: Zohra Bensemra

There have also been other, smaller outbreaks that havedemonstrated the risk that exists at the "interfaces" between human activity and wildlife. One example is Nipah virus disease which has been listed as one of the World Health Organization's top-10 priority diseases.

Dr Brookes said this was first observed in large numbers of pigs on farms in Malaysia.

"There were also bats living in that region as well. And then they plantedfruit trees around the pig farm and so thatencouraged bats to that pig farm inadvertently," she said.

While the bats were already carrying the virus, it wasn't causing the disease in them, so thefirst signs of the disease were actually identifiedin the pigs.

"And then that virus evolved in the pigs because there were many pigs sowhich gave the virusopportunityto multiply and from there it infected humans," she said.

Scientists have zeroed in on areas withhigh livestock density, wildlife encroachment and high human population density as posing ahigher risk of a crossover happening.

Dr Brookes says that's whySouth-East Asia has become an area of focus, "because it ticks those boxes".

But diseases can emerge anywhere.Mosquitoes in North America, camels in Africa, pigs in Europe and monkeys in South Americaalso have been identified as having potential pandemic pathogens.

Poultry too carries risks due to its linkto Influenza A viruses, according to Joerg Henning, an associate professor in veterinary epidemiology at the University of Queensland.

Denis Balibouse, file photo: Reuters

There have also been emerging infectious diseases closer to home in Australia. A 2013 review found at least 20 human diseases associated with disturbed natural environments in Australia alone between 1973 and 2010, including Hendra virus, West Nile virus and Australian bat lyssavirus.

"Australia has had an unusual number of emerging infectious diseases as well," Dr Brookes said.

"I think it might just be down to the fact that we have relatively good surveillance here."

Recent studies have suggested that infectious diseases are emerging a lot more quickly than before, with a reportpublished in 2005 finding that they were appearingin humans every eight months.

AP: Matilde Campodonico

"There is no doubt that there will be other pandemics ahead of us and, in fact, as far as most epidemiologists are concerned, this one was long predicted," Dr Vally said.

Just how devastating the next pandemic will be, however, remains unclear. It will depend on several factors, includingthe infectiousness and the severity of whatever disease is behind it.

"What we do know is that both the drivers for the emergence of new pathogens with pandemic potential are strong and getting stronger," Dr Vally said.

"And we also know that the characteristics of our modern world facilitate the rapid spread of these pathogens when they emerge."

Dr Henningalso said that outbreaks of animal-to-human transmissions have become "more frequent in the last decades", but added "the pandemic is multiplied by the absence of reliable early warning systems and weak public health systems".

The experiences of 2020 and 2021 have taught us ishow the world can better future-proof against other pandemics.

For example, thepandemic has exposed, in wealthy countries as well as poor, "gaps in disease surveillance and disease control,"Dr Vally said.

AP: Emilio Morenatti

Even now, more than a year later, many countries are still grappling with how to control the spread of the coronavirus, particularly in light of new variants.

Dr Brookes said that "as long as countries have massive spread events, we will keep seeing waves of infection".

This is why there's been such a focus on vaccinating populations such as Australia and other middle- to high-income countries.

But Dr Brookes has also raised an issue with this strategy: "We should actually be really thinking about low- to middle-income countries where they don't have the opportunity to quarantine and control the virus like high-income countries do. Vaccination of people in these countries is critical to prevent emergence of new variants."

To be prepared for possible future pandemics, Dr Vally says it is necessary to not only have systems in place ready to kick into action but also to work together across the globe to bring disease threats under control.

"The one shining light during the pandemic is the advances in vaccine development that have occurred and that will not only impact on our ability to combat future pandemics but should also have a significant impact on other diseases in future," he said.

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SARS, MERS, COVID-19 and Disease X? Another pandemic may still be ahead of us. But what could it be? - ABC News