Compared to many other countries in the world, Australia and New Zealand have done an extraordinary job controlling COVID-19.
There are 738 active cases of COVID-19 in Australia. Only 62 were in the hospital.
The situation in New Zealand is similar, with 136 active cases, only two of them in hospital.
If we continue on this path, can we eliminate COVID-19 from Australia and New Zealand?
CONTROL -> ELIMINATION -> ERADICATION
To answer this question, we first need to understand what elimination means in the context of disease, and how it differs from control and eradication.
Disease control is when we see a reduction in disease incidence and prevalence (new cases and current cases) as a result of public health action. Reduction does not mean zero cases, but rather to an acceptable level.
Unfortunately, there is no consensus on what is acceptable. This can differ from disease to disease and from jurisdiction to jurisdiction.
For example, there were only 81 cases of measles reported in Australia in 2017. Measles is considered controlled in Australia.
In contrast, measles is not considered to be controlled in New Zealand, where there was an outbreak last year. From 1 January 2019 to 21 February 2020, New Zealand recorded 2,194 cases of measles.
For disease elimination, there must be zero new cases of disease in a given geographic area. There is no specific period to be maintained – usually depends on the incubation period of the disease (the time between exposure to the virus and the onset of symptoms).
For example, the South Australian government sought 28 days of no new cases of the corona virus (twice the incubation period of COVID-19) before they considered removing it.
Even when a disease has been eliminated, we continue interventions such as border control and surveillance testing to ensure it does not return.
For example, in Australia, we have succeeded in removing rubella (German measles). But we maintain an immunization schedule and disease control program.
Finally, eradication of disease is when there is no worldwide incident of an illness after a deliberate attempt to eliminate it. In this scenario, we no longer need intervention.
Only two infectious diseases have been declared eradicated by the World Health Organization – smallpox in 1980 and rinderpest (disease in cattle caused by paramyxovirus) in 2011.
Polio is nearing eradication with only 539 cases reported worldwide in 2019.
Guinea worm disease is also close to a total of only 19 human cases from January to June 2019 in two African countries.
ANY STAGE WITH COVID-19?
In Australia and New Zealand, we have controlled COVID-19.
What’s important, in Australia, effective reproduction amount (Reff) close to zero. Reff’s estimate comes from mathematical modeling, which has not been published for New Zealand, but Reff is likely close to zero in New Zealand too.
Reff is the average number of people infected by each infected person. So an average of 2 means on average, everyone with COVID-19 infects two other people.
If the Reff is greater than 1, the epidemic continues; if Reff is equal to 1, it becomes endemic (that is, it grumbles permanently); and if the Reff is lower than 1, the epidemic is gone.
So we can be on the road to elimination.
In both Australia and New Zealand we have found almost all cases of imports, quarantined them, and traced contacts. Based on extensive community testing, it also seems that there are very few cases obtained by the community.
The next step in both countries is sentinel surveillance, where random testing is carried out in certain groups. Hopefully in time these results will be able to show us that COVID-19 has been removed.
THIS IS VERY COVID-19 WILL NEVER BE REMOVED
To be eradicated, a disease must be preventable and treatable. At present, we do not have anything to prevent COVID-19 (such as vaccines) or proven treatments (such as antivirals).
Even if a vaccine is available, SARS-CoV-2 (the virus that causes COVID-19) is easily mutated. So we will be in a situation like we are with influenza, where we need annual vaccinations that target circulating strains.
Another factor that makes COVID-19 very difficult if not impossible to eradicate is the fact that many infected people have few or no symptoms, and people can still be transmitted even without symptoms. This makes detection of cases very difficult.
At least with smallpox, it’s easy to see if someone is infected, because their body is covered in pustules (fluid-filled swelling).
So, even though we may be on the path to elimination in Australia and New Zealand, eradication is a different ball game.
This article originally appeared on Conversation and republished with permission