In part eight of our multi-disciplinary Millennium Project series, Martyn Jeggo argues that we must search the animal world for clues if we are to react in time against the rise of new and emerging viruses.
Global challenge 8: How can the threat of new and re-emerging diseases and immune micro-organisms be reduced?
The threat from new and emerging viruses is increasing as these infections continue to spread across the world. In the past 20 years alone, some 30 new, highly infectious diseases have been identified, many of which infect humans – including Hendra and SARS (severe acute respiratory syndrome).
There are no effective treatments for the majority of these diseases, nor are vaccines available to prevent infection.
Understanding the risk
Viruses are uniquely dangerous because of their ability to mutate and change, often becoming more lethal for their existing hosts or enabling them to infect new hosts.
Many of the most dangerous viruses are zoonotic in nature: they spread from animals to humans, often in a highly unpredictable way. This ability to live in a range of hosts and the often rapid speed of transmission make them a deadly threat to people, our livestock and our economic well-being.
The 2003 SARS epidemic was a perfect example of a previously unknown virus causing chaos worldwide as it spread from China around the world. It was subsequently shown that a SARS-like virus had been dormant in bats for some time before a chance mutation occurred that enabled the virus to switch hosts and affect the civet cat – and then spread to humans.
These events brought about by a random virus mutation illustrate the need to keep an open mind when considering what might emerge as the next SARS or influenza pandemic. We shouldn’t, for example, rule out the possibility of wild birds from Asia migrating to the top end of Australia, mingling with our native birds and introducing a new type of influenza we’ve never seen before and therefore have little or no immunity to.
Shifting focus, be prepared
To assist us in preparing for global epidemics, we need to shift focus from responding when diseases emerge, to pre-empting or predicting the event.
For those diseases we’re aware of, we need to find out as much as we can to fully identify the risks they pose to our health and economy. This will allow us to establish mitigation strategies and processes to both reduce the likelihood of an outbreak occurring or reduce the consequences should an outbreak occur.
If diseases are unknown we’re essentially trying to predict the unpredictable. But we can make informed decisions based on what we already know. And this is best achieved through taking a systems-specific, rather than a disease-specific, approach.
In other words, we undertake surveillance not just to look for a specific disease, but to look for unusual events such as a sudden spike in the number of wild bird deaths that would signify that something is amiss, even though it’s not clear what’s wrong.
Another example may be noticing a significant increase in ambulances responding to large numbers of people “feeling ill”. This approach is termed syndromic reporting and is increasingly used to assist in the early warning of a major pandemic or major disease event.
We shouldn’t underestimate the need to be prepared and the power of simulation exercises to both test and further develop our response systems. Despite taking time and resources, these exercises not only critically highlight what is being done correctly but what can be improved, assisting us in preparing for future outbreak events.
Uncertainty is always a characteristic of these new and emerging disease events. Preparing the community prior to a potential disease outbreak will increase the likelihood that management strategies, such as animal or people movement control, are understood and followed.
Australians are aware of the damage that diseases, weeds, invasive animals and insects can inflict on crops, livestock, properties, farm profits and on human health. Biosecurity is all about preventing or keeping the impact of these threats and outbreaks to a minimum.
CSIRO realises the importance of a coordinated approach and is currently reorganising its biosecurity and related research activities to form a National Biosecurity Flagship. This move will further promote collaboration with related research agencies including state, federal and international partners.
Improved coordination of biosecurity research will allow us to better safeguard public health, the environment and the economy into the future. It will also greatly assist other countries as they too strive to deal with the pests and diseases that continue to spread globally and threaten general health.
Population growth, livestock farming practices and climate change have all disturbed the global ecosystem and increased the risk of virus emergence and spread. When you add the huge increase in global travel, you’re left with an ideal opportunity for these virus infections to further spread around the world.
Traditionally, we’ve approached wildlife, animal and human diseases entirely separately. What we need now is to take a “One Health” approach with scientists across all three disciplines working together to understand the system holistically. To deal with zoonotic viruses, for instance, we need to understand the multidimensional links between wild animals, livestock production, the environment and global public health.
Understanding the mechanism of how viruses behave in different animal species and environments and putting this in the context of our ecosystem is perhaps the best approach to predicting and pre-empting future virus risks.
This One Health approach has already been successful in Australia with the development of a horse vaccine against the deadly Hendra virus.
By working together, we realised there wasn’t much we could do to reduce bat populations, and vaccinating people would cost too much and take too long. We soon realised the best opportunity to intervene with the human infection pathway was to vaccinate horses. This will prevent the disease in horses and reduce virus shedding; both of which are critical in reducing the risk of the virus spreading to people.
The reality is that no matter how effective our Australian border controls are, there is always the possibility that micro-organisms will get through. We need to know what systems and management should be in place for dealing with outbreaks of disease, whether caused by viruses, bacteria, fungi or parasites.
But we must remember that pre-empting these biosecurity threats is far less expensive and infinitely preferable than dealing with a disease once it has emerged.
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