Dr Parmjeet Parmar
Auckland, December 9, 2020
Standfirst: Donald Rumsfeld (Former US Secretary of Defence) once said that they could plan for the known unknowns. It was the unknown unknowns that were the greatest risk. Dr Parmjeet Parmar examines that threat in Covid-19, and why it makes the need for serological testing pressing.
A finger prick blood sample as part of an antibody rapid serological test for Covid-19
(Photo: AFP/Getty Images)
A possible source of infection is “known” for the two Auckland women who have tested positive for Covid-19 in the Fiji border quarantine, the Fijian Ministry of Health and Medical Services says.
That is a relief.
The pair tested negative 72 hours prior to leaving Auckland; the new positive results did not come up until tests on day 12 of their managed isolation.
It is believed they were infected on the flight into Fiji, indicating the day 2 test may have been a false negative. However, it is great to fall back on a possible “known” source and that these positives have finally been detected.
Not the first time
This is not the first time when a person from Auckland has tested positive after arriving overseas. For example, a previous case of a woman earlier this year who travelled from Auckland to Sydney had tested positive but that was a completely different scenario.
The source of her infection was “unknown” and it came down to her being deemed a missed asymptomatic case earlier– only suffering from some loss of smell and taste, not meeting the criteria to get tested.
While we realise the importance of “knowns,” every new incident of Covid-19 has presented us an opportunity to explore the “unknowns.”
People largely present themselves for a test only if they have symptoms.
AUT student positive
The only reason that positive AUT student who lives in an apartment block in Vincent Street came to anyone’s attention last month was because she fell ill.
Now that may sound obvious, but with the current approach we are still addressing the “knowns.”
For a minute, imagine, that positive AUT student that caused all the panic was asymptomatic. The consequence would have been no detection and they would’ve gone about their regular routine in the Auckland CBD. Our biggest city would’ve been back at risk, without anyone knowing how or why.
We cannot fool ourselves by dismissing the real risk this new case could have imposed.
We could all have been thrown back to where we started when the whole country was put into level 4 lockdown.
Asymptomatics are spreaders
Various scientific studies around the world have shown that asymptomatics are spreaders too. There are publications suggesting asymptomatics can spread the virus for longer than 14 days. Scientific publications suggest that a person being asymptomatic does not mean that person is carrying less viral copies than one showing symptoms and their capacity to infect others around them should not be underestimated.
For the number of New Zealanders that have no symptoms or weak symptoms, they are none the wiser to their risk of infecting their community.
Not just that, but the virus can mutate anywhere, even in New Zealand.
According to the Ministry of Health on December 5, 2020, we have had 89 such cases making up 4% of total cases so far who contracted the virus within New Zealand but the source is still “unknown.”
About Clusters
In terms of clusters, a cluster as described by the Ministry as a group of “10 or more individuals who likely caught the virus from each other.”
There have been three aged residential care facility clusters of 56, 19 and 51 cases each in Christchurch and Auckland, a private function cluster of 40 people in Auckland, a community cluster of 30 cases in Auckland, and the Marist College cluster of 96 people in Auckland – all starting from sources that are “unknown.”
No single test for Covid-19 assures 100% certainty that the person is not infected.
The possibility of false negatives is a known fact.
Some examples
Examples are the cases of those two Auckland residents in Fiji who tested negative on day two in border quarantine, and in the most recent local Defence Force-related cases.
A Defence Force worker and a person in a neighbouring apartment to the positive AUT student’s apartment first tested negative and finally tested positive. They were chosen to undergo multiple tests only because they were ”known’ as high-risk suspects. This makes the “unknowns” of not suspected, low risk individuals and asymptomatics important.
Defining unknown resources
It also makes the case for more than one type of testing and an approach beyond the current one.
Based on currently available “knowns,” no one can define the role of asymptomatics or false negatives in those local 89 cases or six clusters so far that have “unknown” sources.
The current strategy is good enough only to keep the spread under control but not good enough to find any “unknowns” and assure no exposure to the virus.
The answer may be serological tests, known as antibody tests, that work on blood samples rather than nasal swabs.
This type of test is not publicly available in New Zealand. The blood of someone who has been exposed should have developed antibodies against the virus.
It is the presence, or absence, of such antibodies that the new tests measure.
It is time to review the settings that restrict the availability of serological testing.
It is time to take the next step and set a system for a negative PCR test to be followed up by a serological test to bring some rigour in establishing more “knowns.”
-Published under a Special Agreement with Newsroom.
Dr Parmjeet Parmar holds a doctorate (PhD) in Biological Sciences from the University of Auckland and was employed in the industry. She served as a Member of Parliament on National List from September 2014 to September 2020 and as a Families Commissioner (Member of the Board of Families Commission) from 2013 to 2014. She lives in Auckland.
