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Sri Lanka’s declining COVID-19 cases vs PCR tests: A tale of two curves

ECONOMYNEXT – Sri Lanka’s daily confirmed COVID-19 cases are on the decline, says the health ministry. So is the number of daily PCR tests. Is there a connection? Not really, says the ministry.

Here is a look at the data so far, from the beginning of the second wave in October 2020.

Graphic by Thiyashi Koththigoda

In the latter part of February 2021, a sharp decline was observed in both cases and tests. With the obligatory “correlation does not imply causation” caveat out of the way, are authorities being somewhat premature in their apparent confidence that cases are indeed dropping?

According to ministry officials who spoke to EconomyNext, the reason for this sudden dip in confirmed positives was what he called the stringent control of the locally identified clusters: namely the Brandix cluster that was said to be the epicenter of the second wave (though its precise origin is still unclear), the Peliyagoda fish market cluster that came in its wake and a number of sub-clusters that followed.

As to the decline in testing, authorities have offered an explanation that may sound convoluted at first. Denying allegations that testing had seen an alarming drop, a health ministry official claimed earlier this week that the “aggressive” containment of the current clusters and ongoing contact-tracing efforts have contributed to a drop in close contacts which has, in turn, led to the reduction in testing. A majority of PCR tests that have been conducted so far in the island were of close contacts of confirmed cases, the official said on condition of anonymity.

Others disagree. A spokesman for a government lab technologists’ collective said on February 10 that Sri Lankan authorities have “given up” on continuing PCR tests and numerous issues that have cropped up in supply chain management have caused the sharp drop in daily PCRs.

Director of the Institute for Health Policy Dr Ravindra Rannan-Eliya tweeted on Tuesday that testing in the western province had “collapsed”.





The health ministry official, however, maintained that the vaccination programme has no effect on PCR testing, adding that enough staff and technicians are present at hospitals to conduct the tests and run the PCR machines.

“Other than ongoing testing of close contacts, the ministry is continuing random PCR testing island-wide. This has not stopped,” the official said, though it is unclear where such testing is happening at present.

In a period of 24 hours that ended at 6am today, Sri Lanka conducted 9,697 PCR tests, bringing total tests in the island to 2.5 million. With 271 people testing positive for the virus yesterday, total cases in the country have reached 91,289. (Colombo/Mar26/2021)

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