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Random sampling results point to potential spread of virus in community

Random sampling conducted by the Gibraltar Health Authority over the past week suggests up to 800 people may have been infected with Covid-19 during the same period, many of them without symptoms at the time.

The analysis was extracted from initial data following conclusion of the sample and was revealed by Dr John Cortes, the Minister for Public Health, at the 4pm press conference on Good Friday.

Of the 400 random swabs taken, results with just four tests outstanding show just 10 confirmed cases, nine of them active and one recovered.

Extrapolated to the community as a whole, that would indicate up to 800 people infected, or , or 2.5% of the population.

“It’s something like an opinion poll of course, so it is only an indication of the real picture, but a useful one nonetheless,” Dr Cortes said.

Of the potential 800 cases, “…117 have been detected from the 111 calls and from people who have presented, that’s 14.5% of the number [if extrapolated] we suspect are in the community.”

“This could indicate as expected that there’s a considerable number of symptom-free carriers.”

“Indeed six of the 10 positives in the random samples did not have symptoms.”

Dr Cortes said those without symptoms could be expected to develop symptoms over the next week to 10 days, meaning a surge in numbers was not just possible, but likely.

He said that while the lockdown measures appeared to be working in slowing down the rate of infection, there was no room for complacency, particularly given developments in Spain and the UK.

“Public Health advice remains that we will see a surge in hospitalisation, probably next week, as those affected in the community develop symptoms,” he said.

“The potential remains that the hospital could fill up in just a few days, as has been seen in most other countries.”

“We are fortunately ready for this.”

Dr Cortes said the total number of swabs - including both random tests and those targeted at symptomatic people - was now 1543, of which 1492 results had been received and 51 were pending.

There were a total of 127 confirmed cases, of which 58 remained active, most at home in self-isolation, and 69 were recovered.

The results of the random test were also analyses by age and showed that while 17% off those under the age of 70 were positive, only 5.5% of the over 70s had the virus.

“This is a statistically significant result, showing that our strategy of locking down the over 70s early has worked and that for the very large part, they are protecting themselves,” Dr Cortes said.

The results of swabs are now being processed in Gibraltar, ensuring a faster turnaround.

But worldwide shortages of the re-agents needed for the tests means swabbing will still be mostly targeted at those showing symptoms, although further random testing has not been ruled out.

Dr Cortes added too that rate of incidence of positive results had slowed over the period of the lockdown and appears to have peaked between March 26 and March 28, dropping steadily since.

One analysis suggests that whereas Gibraltar currently has 127 positives, that figure could have been closer to 1800 had the lockdown measures not been taken.
“Once again this shows the effectiveness of our measures - and the importance of everyone keeping to the rules,” Dr Cortes said. 

“If we stop applying the restrictions now we will get a surge in cases.”
“We are of course actively considering when and how the measures can be relaxed.”

“It’s a complex challenge facing authorities around the world."
“I am confident that as we monitor the development of the disease in Gibraltar, as we have up to now, we will be able to release in a responsible and measured way, to ensure our health service is not overwhelmed so that we can return to normality as soon as possible.”

“But it can’t be just yet.”

“There is still prevalence in the countries around us, and the majority in the community are not yet immune.”

"We will have to wait and see so that we strike the right balance.”

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