Fish in a pond: swab now, less COVID-19 later says chief Malta virologist

Like Trump, hotelier Michael Zammit Tabona thinks Malta should stop ‘over-testing’ for COVID-19 because of a higher detection of infections. The experts disagree: higher detection is key to reduce COVID-19 cases by removing the infected from circulation

Virologist Chris Barbara (centre): high rate of swabbing is key to Malta’s successful containment
Virologist Chris Barbara (centre): high rate of swabbing is key to Malta’s successful containment

For Dr Chris Barbara, Malta’s most prominent virologist, Malta’s high rate of swab tests is something we should be proud of. “It is the key to Malta’s successful containment of the disease during the first wave and probably the key to recovery from the second wave,” Barbara says.

Recalling advice given by the World Health Organisation, at the onset of the pandemic – “swab, swab, swab” – Barbara says a significant financial investment and round-the-clock work of health workers has allowed Malta to follow this advice to the letter. Malta has now achieved the third-highest swabbing rate in Europe after Luxembourg and Denmark. And the number of tests reached an all-time high this week, increasing from 500 in the beginning April to over 3,000 now.

Barbara praises his eight-person team, describing them and other health officials involved in contact-tracing as “heroes engaged in the frontline in keeping the virus at bay”.

Earlier last week, the hotelier Michael Zammit Tabona, no a stranger to controversy with comments that recently cost him his resident-ambassadorship for Finland, railed against over-testing of COVID-19 cases for detecting a higher rate of infected people.

But Barbara’s logic in defending high swabbing rates is impeccable: “The more swabs you take today, the more infected people you detect and isolate from the community. This is why swabbing is not a statistical census to measure the people infected by COVID-19 but an effective tool in reducing numbers. For the more people you swab now, the less cases of COVID-19 you will have in the next weeks, simply because you would have removed more infected fish from the pool, which would otherwise have infected more fish.”

This is why swabbing alone is not enough. It has to be accompanied by contact-tracing to test and isolate those who potentially have come in contact with the people found positive for the virus. The more infected people are removed from the pool the less the chances of infection for other fish swimming in the same pool.

Chris Barbara again uses a fishing analogy for swabbing, comparing to catching fish with a net. “When someone is found positive, you would not have just caught one person in the net, you would have caught all the potentially infected persons in his or her circle. The more people you isolate, the less infected fish there are swimming in the pool. In this way the numbers start decreasing.”

Barbara admits that the task was easier during the first wave of COVID-19 when Malta closed its ports and airports, in a way that no new infected fish could find themselves in the pool. At that time people were also strictly adhering to social distancing, minimising the risk of infection amongst those still swimming in a pool, which had been isolated from the rest of the world.

“We had reduced active cases to just two, by removing nearly all the infected fish from the pool. We were so close to becoming COVID-free!

“But the opening of airports and the relaxation of social distancing meant that a few contaminated fish managed to get through in to the pool, managing to contaminate many more fish in a way that the situation deteriorated rapidly in just a few days.”

But swabbing, together with mitigation measures like limiting entry to the country to people certified COVID-free, is the key to reducing the numbers again. Barbara acknowledges that in the short term, conducting more tests now means detecting more cases of infections.

“Temporarily you will detect more cases, but this means that in the long term you will find less cases. It is true that on one particular day we had 72 cases. But this meant that all these people and their immediate circle were quarantined and thus stopped from infecting others. If we had not swabbed all these people our hospital will be already flooded by infected people and more vulnerable people would have been exposed to infection….”

Swabs also serve to protect the most vulnerable. “For example, Malta is one of the few countries where everyone who is to be operated at Mater Dei Hospital, is tested,” Barbara says.

Barbara is cautiously optimistic that the large number of swabs, coupled with more restrictions on travel from abroad and transmission hotspots like clubs, will result in a decrease in numbers. “I hope that we will eventually start detecting less cases which means that there will be less contaminated ‘fish in the pool’.”

Daily tests per 1,000 inhabitants 

Luxembourg 5.25
Denmark 2.92
Malta 2.84
UK 2.03
Greece 1.95
Belgium 1.73
Portugal 1.36
France 1.15
Lithuania 1.09
Germany 0.98

The politics of swabbing

In June, US President Donald Trump “sarcastically” claimed that a decrease in coronavirus testing would lower U.S. infection rates.

While Malta prime minister Robert Abela had often referred to the high rate of testing to explain the spike in Malta, he has promised to continue investing and increase the tests “and not do as other countries have done where they have reduced the tests to keep the numbers low”.

But are countries which increase the number of tests detecting a higher number of infected people, liable to be exposed to travel bans from other countries? Luxembourg conducts an aggressive mass-testing programme which its government says has led to the country being unfairly penalised by fellow EU member states.

Luxembourg, which has a population of about 625,000 people, is at the top of the world swabbing rankings, ahead of the United Arab Emirates, Bahrain, Malta and Denmark.

But the success of the scheme has revealed an infection rate that has prompted several European countries, including Germany and the UK, to place it on a travel blacklist.

But the relationship between more testing and new cases isn’t always straightforward. In Finland, health workers doubled the number of tests carried out in the space of a month, and found that positive cases ticked downward. Likewise in the U.K. and Portugal: these numbers suggest that in these countries the disease is under control and testing is simply confirming that this is the case.

So while more tests are likely to detect more cases when the virus is still spreading in the community, as soon as the spread is controlled, swabs will detect less and less cases of infections as was the case in Malta last month when it was very close to being COVID-19 free.