Eradication, elimination, suppression: let’s understand what they mean before debating Australia’s course

Proudly supported by

  Last updated July 28, 2020 at 2:27 pm

Topics:  

Australia’s response to COVID-19 is back in the spotlight, with experts debating whether we should shift gears from a suppression strategy to an elimination strategy.


response to COVID-19_covid-19 lockdown_covid restrictions

Credit: Daniel Pockett/AAP




Why This Matters: The right response to COVID-19 can effectively guide us through the COVID-19 pandemic.




The current surge in community transmission of COVID-19 in Victoria has brought renewed discussion of whether Australia should maintain its current “suppression” strategy, or pursue an “elimination” strategy instead.


But what do these terms actually mean, and what are the differences between the two?


In theory


Disease eradication means a global absence of the pathogen (except in laboratories). We achieved this for smallpox in 1980. Diseases suitable for eradication are usually those where humans are the only host, and where there’s an effective vaccine or other prevention strategy.


Disease elimination relates to a country or a region, and is usually defined as the absence of ongoing community (endemic) transmission.




Also: COVID-19 pandemic: Where to from here?




Elimination generally sits in the context of a global eradication goal. The World Health Organisation sets a goal for eradication, and countries play their part by first achieving country-wide elimination.


Cases and small outbreaks may still occur once a disease is eliminated — imported through travel — but these don’t lead to sustained community transmission.


Finally, disease control refers to deliberate efforts to reduce the number of cases to a locally acceptable level, but community transmission may still occur. Australia’s current suppression strategy, though seeking to quash community transmission, can be classified as disease control.


response to COVID-19_covid-19 restrictions_coronavirus testing

There are subtle differences between disease control, elimination, and suppression. The best response to COVID-19 can also vary. Credit: Bianca De Marchi/AAP


In practice


Elimination and suppression strategies employ the same control measures. For COVID-19, these include:



  • rapid identification and isolation of cases

  • timely and comprehensive contact tracing

  • testing and quarantining of contacts

  • varying degrees of social distancing (lockdown, banning mass gatherings, keeping 1.5m distance from others)

  • border controls: restricting entry through travel bans, and quarantine of returning international travellers

  • face masks to reduce transmission.


The differences between a suppression strategy and an elimination strategy are the strictness, timing, and duration with which these measures are applied, especially travel restrictions.


For example, under a suppression strategy, physical distancing requirements might be lifted while there’s still a low level of community transmission. But under an elimination strategy, these measures would remain in place until there’s no detectable community transmission.


What’s realistic for COVID-19?


First, the prospect of eradicating COVID-19 is likely no longer feasible, even with a vaccine.


People without symptoms may be able to spread COVID-19, which makes it difficult to identify every infectious case (SARS, for example, was only spread by people with symptoms). And if the virus has an animal host, animal reservoirs would also need to be eradicated.




Also: How do viruses jump species? And are spillovers becoming more common?




So what about elimination?


For measles, elimination is defined as the absence of endemic measles transmission for more than 12 months. Countries must demonstrate low incidence, high quality surveillance and high population immunity.


Imported cases in unvaccinated returning travellers and occasional small outbreaks continue to occur, but a country will lose its elimination status if community spread lasts longer than one year.


The majority of the Australian population are immune to measles, which lowers the probability of sustained outbreaks. But most Australians remain susceptible to COVID-19.


So future sustained outbreaks, like the current Victorian outbreak, will remain possible until we can vaccinate the population — even under an elimination strategy.


Like we have with measles, for COVID-19, we need a definition of elimination with specific criteria that can be measured.


Declaring COVID-19 “eliminated” after the absence of community transmission for a few weeks means little during a pandemic, and may lead to complacency in the community. This period should be more like a few months.


Effective suppression can lead to elimination


While the federal government continues to advocate for its suppression strategy, some states have demonstrated absence of community transmission.


International arrivals to these states (and to New Zealand) are comparatively small, and the virus was always going to be more difficult to contain in cities with substantial international arrivals and high population densities, such as Sydney and Melbourne.


To achieve and sustain national elimination of any infectious disease during a pandemic is ambitious. It requires an epidemiologic definition with measurable criteria, significant resources and almost complete closure of international borders.


But maintaining the right for Australian citizens and residents to return to Australia means the borders are never fully closed, whether under a suppression strategy or elimination strategy.


So ultimately, both strategies are susceptible to outbreaks of COVID-19 in the community as long as the pandemic endures.


response to COVID-19_covid-19 restrictions_returned travellers

Returned travellers can threaten elimination and need to be considered in our response to COVID-19. Credit: Bianca De Marchi/AAP


It will always ebb and flow


An elimination strategy would not necessarily have prevented the current outbreak in Victoria, particularly if social distancing restrictions had already been lifted.


Whether Australia continues with its suppression strategy or opts to switch to a defined elimination strategy, either approach will require continued vigilance. This could include intermittent reinstating of restrictions or targeted containment around hotspots as transmission ebbs and flows.


And whatever name we give to Australia’s approach, neither Victoria or New South Wales have accepted any level of community transmission. Both have gone hard to stop community outbreaks that have arisen, and that’s a good thing.


But long-term maintenance of periods of elimination are unlikely to be possible until we have a vaccine.


This article was co-authored with Anita Heywood from UNSW.


This article is republished from The Conversation under a Creative Commons license. Read the original article.


More Like This


The race is on around the world for a COVID-19 vaccine


Headlines promise we’re on the ‘cusp’ of defeating coronavirus – we’re not and it’s too soon to relax restrictions




About the Author

Raina MacIntyre
Professor Raina MacIntyre is NHMRC Principal Research Fellow and Head of the Biosecurity Program at the Kirby Institute, and Professor of Global Biosecurity at UNSW.

Published By

Featured Videos

Placeholder
Big Questions: Cancer
Placeholder
A future of nanobots in 180 seconds
Placeholder
Multi-user VR opens new worlds for medical research
Placeholder
Precision atom qubits achieve major quantum computing milestone
Placeholder
World's first complete design of a silicon quantum computer chip
Placeholder
Micro-factories - turning the world's waste burden into economic opportunities
Placeholder
Flip-flop qubits: a whole new quantum computing architecture
Placeholder
Ancient Babylonian tablet - world's first trig table
Placeholder
Life on Earth - and Mars?
Placeholder
“Desirable defects: Nano-scale structures of piezoelectrics” – Patrick Tung
Placeholder
Keeping Your Phone Safe from Hackers
Placeholder
Thru Fuze - a revolution in chronic back pain treatment (2015)
Placeholder
Breakthrough for stem cell therapies (2016)
Placeholder
The fortune contained in your mobile phone
Placeholder
Underwater With Emma Johnston
Placeholder
Flip-flop qubits: a whole new quantum computing architecture
Placeholder
The “Dressed Qubit” - breakthrough in quantum state stability (2016)
Placeholder
Pinpointing qubits in a silicon quantum computer (2016)
Placeholder
How to build a quantum computer in silicon (2015)
Placeholder
Quantum computer coding in silicon now possible (2015)
Placeholder
Crucial hurdle overcome for quantum computing (2015)
Placeholder
New world record for silicon quantum computing (2014)
Placeholder
Quantum data at the atom's heart (2013)
Placeholder
Towards a quantum internet (2013)
Placeholder
Single-atom transistor (2012)
Placeholder
Down to the Wire (2012)
Placeholder
Landmark in quantum computing (2012)
Placeholder
1. How Quantum Computers Will Change Our World
Placeholder
Quantum Computing Concepts – What will a quantum computer do?
Placeholder
Quantum Computing Concepts – Quantum Hardware
Placeholder
Quantum Computing Concepts – Quantum Algorithms
Placeholder
Quantum Computing Concepts – Quantum Logic
Placeholder
Quantum Computing Concepts – Entanglement
Placeholder
Quantum Computing Concepts - Quantum Measurement
Placeholder
Quantum Computing Concepts – Spin
Placeholder
Quantum Computing Concepts - Quantum Bits
Placeholder
Quantum Computing Concepts - Binary Logic
Placeholder
Rose Amal - Sustainable fuels from the Sun
Placeholder
Veena Sahajwalla - The E-Waste Alchemist
Placeholder
Katharina Gaus - Extreme Close-up on Immunity
Placeholder
In her element - Professor Emma Johnston
Placeholder
Martina Stenzel - Targeting Tumours with Tiny Assassins
Placeholder
How Did We Get Here? - Why are we all athletes?
Placeholder
How Did We Get Here? - Megafauna murder mystery
Placeholder
How Did We Get Here? - Why are we so hairy?
Placeholder
How Did We Get Here? - Why grannies matter
Placeholder
How Did We Get Here? - Why do only humans experience puberty?
Placeholder
How Did We Get Here? - Evolution of the backside
Placeholder
How Did We Get Here? - Why we use symbols
Placeholder
How Did We Get Here? - Evolutionary MasterChefs
Placeholder
How Did We Get Here? - The Paleo Diet fad
Placeholder
How Did We Get Here? - Are races real?
Placeholder
How Did We Get Here? - Are We Still Evolving?
Placeholder
How Did We Get Here? - Dangly Bits
Placeholder
Catastrophic Science: Climate Migrants
Placeholder
Catastrophic Science: De-Extinction
Placeholder
Catastrophic Science: Nuclear Disasters
Placeholder
Catastrophic Science: Storm Surges
Placeholder
Catastrophic Science: How the Japan tsunami changed science
Placeholder
Catastrophic Science: How the World Trade Centre collapsed
Placeholder
Catastrophic Science: Bushfires