Time to rethink our COVID-19 testing strategy

*I am reposting here with some edits and added links the article I wrote in the Daily Mirror on 7th October 2020.

The Minuwangoda incident should come as no surprise. The problems were obvious with the Kandakadu outbreak, but I remained silent in the hope that lessons would be learnt, but it seems that I was wrong.

We must recognise that as long as the global COVID-19 pandemic continues, we can never declare final victory against COVID-19 in Sri Lanka. To do so is to fool ourselves and the public. Wise leaders, like Jacinda Ardern, the New Zealand PM, warned their nations not to let their guard down, even after months of no local cases, because they understood that (a) no set of border controls can be 100% guaranteed to keep the virus out; and (b) it is impossible to know with certainty that there is no COVID-19 virus circulating unseen in
the community.

As long as we allow international arrivals, there is a constant risk that the virus will creep in undetected and spark a local outbreak or worse, a second wave. The gold standard for detecting the virus, the PCR swab test, is not 100% perfect. Done properly and at the optimal time, the test still fails to detect the virus 10-20% of the time. Compounding this, is that we know now that many people infected by the COVID-19 virus never experience any symptoms. This is mostly in the case of younger adults. None of this would matter if those who test negative or have no symptoms are not infectious, but it turns out that they are.

This means that however good our airport quarantine procedures are, it is always possible that a positive case will get through and later cause a hidden outbreak.14 days observation of arrivals during quarantine for any symptoms, plus two PCR tests, plus 14 days home isolation is not 100% guaranteed to pick up all infected cases.This is not an issue of competence. It simply reflects the biology of the virus.

“In the Kandakadu camp, it is reported that many infected residents developed coughs and colds and were seen by doctors, but none were tested until the outbreak had infected hundreds”

Back in May, the potential leakage of cases through quarantine or by the infection of airport and quarantine workers by arrivals was a theoretical risk, but it is no longer that. Almost all countries that crushed the first wave of COVID-19 and also implemented tough border quarantine policies to prevent the virus coming back, have faced new outbreaks caused by international arrivals. This includes China, Vietnam, Australia, New Zealand, Bhutan, Hong Kong and others. And the fact that we have depended for so long on exporting lakhs of our people to work in low-end jobs in countries that are now rife with COVID-19 means that our returnees are far more likely to be infected than those returning to China, Vietnam and these other countries.

A single, undetected imported case will lead in time to a new outbreak, and potentially a second wave. The big problem is that the virus can spread silently for a long time, exponentially widening the circle of infected people, before anyone falls sick enough to require treatment and to provoke a doctor to order a PCR test. As I mentioned, in many people the virus causes no illness or symptoms, and in those it does cause symptoms, these are often so trivial or short-lived that the affected person would never think of going to the doctor. The experience here in Sri Lanka (think Minuwangoda or Kandakadu) and also in other countries which beat the first wave, is that an invisible outbreak caused by a single case can spread for weeks and infect hundreds before detection.

The good news is that we don’t need lockdowns or to close schools or seal our borders to manage and defeat these outbreaks. Other countries have shown that an effective strategy to manage this risk is intensive, continuous testing of people in the community who have respiratory symptoms or fever, as these are the people most likely to have the virus. This works because, even if most COVID-19 infected people experience no symptoms, some do, and some of these will inevitably have symptoms bad enough to make them see a doctor. So, in a hidden COVID-19 outbreak, it is only a matter of time before an infected person develops a fever or a cough or some other symptom.

Hong Kong tests all patients at its government OPD clinics with these symptoms, plus others at private GP clinics. This might seem impossibly expensive, but rich Hong Kong doesn’t waste money like us getting doctors to do swab tests on these patients, instead it simply gets patients to cough and spit into plastic containers, which they can even do at home in private, a method that our own Prof. Malik Peiris in Hong Kong has encouraged us to follow. Other countries, like China,Vietnam, Australia and New Zealand, still rely on traditional swabs, but they actively encourage people with fever, coughs and colds to get tested.

In theory, our health ministry already does this, but it is small scale, not systematic and more importantly, not adequate. In the Kandakadu camp, it is reported that many infected residents developed coughs and colds and were seen by doctors, but none were tested until the outbreak had infected hundreds. In the Minuwangoda incident, where hundreds have been infected, I wouldn’t be surprised if no one ever had any symptoms. We can compare this with recent outbreaks in China, Vietnam and New Zealand, where typically only dozens or fewer were infected by the time the health authorities detected the outbreak. All these countries then typically crushed their outbreaks within weeks, and not months as in the case of Kandakadu, because they stepped up testing far more aggressively in response than we have done.

“An adequate testing strategy in Sri Lanka probably means increasing testing in the community to around 5-8,000 tests a day, and more if there is an ongoing outbreak”

So, what is an adequate level of testing to detect and crush these hidden outbreaks quickly? Unfortunately, we need to ignore the WHO advice on this, and look seriously at what the other successfull countries that crushed the first wave are doing. If one takes New South Wales in Australia which has managed to successfully avoid a second wave by encouraging people to voluntarily seek testing even for a “scratchy throat”, it did 150,000 PCR tests in the community of its 8 million people in the past two weeks, despite only picking up two cases. And it’s not just rich countries like Australia and New Zealand, countries such as Vietnam and China do similar rates of testing. This compares with probably less than 25,000 PCR tests done in Sri Lanka’s 22 million people in the past two weeks. An adequate testing strategy in Sri Lanka probably means increasing testing in the community to around 5-8,000 tests a day, and more if there is an ongoing outbreak.

We need to recognise that incidents like Kandakadu and Minuwangoda demonstrate gaps in our strategy and start taking testing seriously, learning from those who are doing better. And this does not mean more random testing in the community, which is a hundred times less likely to detect new cases than testing people with symptoms. We need to start systematically testing patients with respiratory symptoms or fever without obvious cause and encouraging the public with such symptoms to come forward for testing.
Not to do so is to continue playing Russian roulette with the hard won achievement of the government in crushing the first wave, the lives of our people, our businesses, government tax revenues, and the education of our children.

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